Lojban grammar

Lojban is a constructed, human-speakable language, based on predicate logic. It is one of the latest and most comprehensive languages on the earth in that it was designed in 1987 succeeding such experimental predecessors as Esperanto, Ido, Loglan, and Láadan etc., as well as deriving its root words from the 6 widely spoken natural languages, Arabic, Chinese, English, Hindi, Russian, and Spanish. The characteristic regularity, unambiguity, and versatility of Lojban grammar owes much to the fact that its creation followed the development of scientific linguistics and computer programming, the fruits of which Esperanto and Loglan could not have drawn on as their design principles. Its linguistic advantage can be summarized as follows: "Lojban moves beyond the restrictions of European grammar. It overtly incorporates linguistic universals, building in what is needed to support the expressivity of the whole variety of natural languages, including non-European ones."

Phonology

6 vowels and 21 consonants exist in Lojban. The phonemes are to be commensurate with graphemes, which means Lojban is to have 27 letters (lerfu) corresponding to each piece of sound in the language. Lojbanic graphemes can vary in mode; this article employs the Latin alphabet version, which is currently in the most common usage (see Orthography for more detail). The phonemes, on the other hand, are defined solely by International Phonetic Alphabet.

The tables below show typical realizations of sounds and the Latin alphabets in Lojban. In all cases except the tap/flap consonant the first phonemes represent the preferred pronunciation. The second or third phonemes are the permitted variants intended to cover dissimilitude in pronunciation by speakers of different linguistic backgrounds.

Basic sounds

	Phoneme	Grapheme
vowel
open	a (ɑ)	a
front mid	ɛ (e)	e
front close	i	i
back mid	o (ɔ)	o
back close	u	u
central mid	ə	y
fricative
voiceless labial	f (ɸ)	f
voiced labial	v (β)	v
voiceless velar	x	x
unvoiced glottal / unvoiced dental	h (θ)	'
sibilant
voiceless alveolar	s	s
voiced alveolar	z	z
voiceless coronal	ʃ (ʂ)	c
voiced coronal	ʒ (ʐ)	j
stop
voiceless bilabial	p	p
voiced bilabial	b	b
voiceless dental / voiceless alveolar	t	t
voiced dental / voiced alveolar	d	d
voiceless velar	k	k
voiced velar	g	g
glottal	ʔ	.
approximant
labial glide	w	u-
palatal glide	j	i-
voiced lateral	l (l)̩	l
nasals
voiced bilabial	m (m)̩	m
voiced dental / voiced velar	n (n̩, ŋ, ŋ̩)	n
tap/flap
rhotic	r, ɹ, ɾ, ʀ, r ̩, ɹ̩, ɾ̩, ʀ̩	r

Diphthongs

Lojban has 16 diphthongs (a kind of sound which consists of a vowel plus a glide, always constituting a single syllable). The combinations <ai>, <au>, <ei> and <oi>, for instance, are all realized as the corresponding falling diphthongs. To force these sounds to be pronounced separately as monophthongs, a comma can be put between them. Triphthongs do not exist in Lojban.

Allophones

The vowels can be either rounded or unrounded. And the consonants can be either aspirated or unaspirated, but not palatalized in general. The voiceless stops /p/, /t/ and /k/ are usually aspirated, but need not be. The affricates /ʤ/ (the voiced postalveolar affricate), /d͡z/ (the voiced alveolar affricate), /tʃ/ (the voiceless postalveolar affricate) and /t͡s/ (the voiceless alveolar affricate) also occur in Lojban, but are each considered to be a combination of the appropriate phonemes in the language (being the realization of <dj>, <dz>, <tc> and <ts>, respectively). The rhotic sounds are all equally acceptable as an identical phoneme. <l>, <m>, <n>, and <r> may be syllabic.

Buffering of consonant clusters

For those who, given their native language background, may have trouble pronouncing (certain) consonant clusters, there is the option of inserting buffer vowels between them, as long as they differ sufficiently from the phonological vowels and are pronounced as short as possible. Possible choices include [ɪ], [ɨ], [ʊ] and [ʏ] (but not [y], which is the rounded counterpart of [i] and thus a valid realization of <i>). The resulting added syllables are completely ignored by the grammar, including for the purposes of stress determination.

Orthography

Lojban may be written in different orthography systems as long as it meets the required regularities and unambiguities. Some of the reasons for such elasticity would be as follows:

1. Lojban is rather defined by the phonemes (spoken form of words), therefore, as long as they are correctly rendered so as to maintain the Lojbanic audio-visual isomorphism, a representational system can be said to be an appropriate orthography of the language;
2. Lojban is meant to be as culturally neutral as possible, so it is never crucial or fundamental to claim that some particular orthography of some particular languages (e.g. the Latin alphabet) should be the dominant mode.

Some Lojbanist extends this principle so as to claim that even an original orthography of the language is to be sought.

Note: It is suggested that the Lojban term lerfu be used instead of the English so that confusion with letter, the kind one writes to someone, is avoided (James Cooke Brown's version was letteral by analogy with numeral). This section will be in accordance with that discernment.

Latin/Roman mode

Lojban's Latin alphabet consists of 23 lerfu a b c d e f g i j k l m n o p r s t u v x y z plus 3 semi-lerfu ' , . . They are intentionally ordered in accordance with that of ASCII characters.

Capitalization may be applied to mark a non-standard stressed syllable as in cmene, but they are not considered separate lerfu. Whether a single vowel or the entire syllable is capitalized is a matter of preference; for example, the name "Josephine" can be rendered as either DJOzefin. or djOzefin. (without the capitalization, the ordinary rules of Lojban stress will cause the 'ze' syllable to be stressed instead).

Punctuation marks are not mandatory; such notions as question or exclamation are expressed with words rather than unpronouncible symbols.

Cyrillic mode

This mode was conceived when the introductory Lojban brochure was translated into Russian. 23 lerfu а б в г д е ж з и к л м н о п р с т у ф х ш ъ plus 3 semi-lerfu ', . are used. The hard sign ъ is assigned to the open-mid vowel. Diphthongs are written as vowel pairs, as in the Roman mode.

Tengwar mode

Kena argues for the Tengwar writing of Lojban, insisting that:

1. the Latin alphabet is too strongly related to western civilizations, and thus probably introduces some kind of cultural bias in Lojban. Lojban wants to be both logical and culturally neutral, the tengwar already are;
2. the tengwar system inherently contains some main Lojban morphology rules, making Lojban easier to learn when it is written with tengwar.

Exemplary mappings between the Tengwar system and the Lojban sounds are provided as follows: [2], [3].

Advocates of this include Eric S. Raymond.

Japanese mode

A Japanese hiragana version of Lojban orthography has been proposed, in which case more than 80 lerfu may by used. This mode is not without certain technical issues since the hiragana (and katakana too) are always syllabary indicating an open syllable except the "n" sound, requiring the practicer some special attention when representing the Lojbanic consonant clusters. Experimental transcription rules are given by Fa-Kuan's website. Examples of Lojban haiku compositions in the orthography can be found at following links: [4] [5].

Morphology

Lojban has 3 word-classes: brivla (predicate words), cmavo (structure words), and cmene (name words). Each of them has uniquely identifying properties, so that one can unambiguously recognize which word is of which part of speech in a string of the language. They may be further divided in sub-classes (discussed respectively below). There also exists a special form called rafsi assigned to some of the brivla and cmavo.

brivla

brivla carry the content (semantic information) of an expression, which means their function may be roughly analogous to common noun, verb, adjective, or adverb in natural languages (although some modal cmavo too may have adverbial purposes). brivla may be identified by the following properties:

• Have more than one syllable
• Are penultimately stressed
• Have a consonant cluster (at least two adjacent consonants) including the second consonant
• Start with a consonant (except some fu'ivla), end with a vowel

Such a word like lobypei will still be considered as a brivla because the special gluing vowel y between b and p is to be ignored and therefore a consonant cluster (b-p) assumes its existence within it.

Unlike its natlang counterparts mentioned earlier, brivla do not inflect for tense, person, or number.

brivla's sub-classes are as follows, with some examples.

gismu

The simplest brivla which constitute the lexical base of the language is called gismu. They are invariably five-letter, which distinguishes it from the other types of brivla, and are in a form of either CVCCV or CCVCV (C stands for a consonant and V for a vowel). Being two syllables means that the general rule of brivla to be stressed penultimately will always cause the first syllable to be stressed.

viska (CVCCV)

prami (CCVCV)

They have been chosen or added as root words bacause they a) represent concepts that are very familiar and basic, b) represent concepts the usage of which is equally frequent among different languages, c) would be helpful in constructing more complex words, or d) represent fundamantal grammatical concepts of Lojban like cmavo and gismu. The main source languages from which they were drawn are Arabic, Chinese, English, Hindi, Russian, and Spanish. Here is further explanation of the nature of gismu by Cowan:

The gismu do not represent any sort of systematic partitioning of semantic space. Some gismu may be superfluous, or appear for historical reasons: the gismu list was being collected for almost 35 years and was only weeded out once. Instead, the intention is that the gismu blanket semantic space: they make it possible to talk about the entire range of human concerns. [...] For a given concept, words in the six languages that represent that concept were written in Lojban phonetics. Then a gismu was selected to maximize the recognizability of the Lojban word for speakers of the six languages by weighting the inclusion of the sounds drawn from each language by the number of speakers of that language.

The Complete Lojban Language: 4.4

According to Robin Turner, the creation was done by computer.

Approximately 1350 gismu exist, which is a relatively small number when compared to that of English words ranging from 450,000 up to 1,000,000. Theoretically, by learning only these root words, as well as their fragmental forms and some major structure words (cmavo), one will be able to communicate effectively in Lojban.

lujvo

The compound form of brivla is called lujvo.

pazvau (panzu + vasru)

bavlamdei (balvi + lamji + djedi)

seljgi (se + jgira)

fu'ivla

A borrowed-word type of brivla. They usually refer to things that are culture-specific or to kinds of plants or animals, concepts which cannot be easily expressed as mere modifying-modified combinations of Lojban's internal root words.

fu'ivla can be subdivided into four types according to the extent to which they are modified, namely Stage 1, 2, 3, and 4 fu'ivla.

Stage 1 fu'ivla

The longest form, quoting a foreign word/phrase while preserving its original spelling with particular structure words.

me la'o ly. spaghetti ly.
(la'o indicates that a non-lojbanic text follows. ly. are delimitters of that foreign text. And me turns the whole sequence into a selbri so that the word/phrase can form a bridi with its given place structure. In this example, "x1 is a quantity of spaghetti" is a possible place structure.)

Stage 2 fu'ivla

This stage involves lojbanizing the sound and spelling of the word.

me la spagetis.
(me is still needed since la spagetis. cannot by itself work as a brivla.)

Stage 3 fu'ivla

At this stage a borrowed word is fully turned into a single brivla, having its own place structure. Since every brivla is not permitted to have more than one meaning, it is often the case that they are attached by a rafsi (with a hyphen like "-r-", "-n-", or "-l-") categorizing or limitting the semantic scope of the word (such are called "rafsi classifier"). Again they always start with a consonant and end with a vowel.

cidjrspageti (using longer rafsi: cidj + r + "spaghetti")

djarspageti (using shorter rafsi: dja + r + "spaghetti")

zgikrtekno (zgike + "techno")

runrxorigami (rutni + "origami")

Stage 4 fu'ivla

These are the borrowings which are so common or so important that have become as short as possible, having no rafsi classifier. Unlike other brivla, they may begin with a vowel (preceded by a pause mark separating it from the previous word). Also the word must not be of a form that one can remove all the initial vowels (and apostrophes) and have a valid word.

skalduna ("Basque" from "euskaldun")

frangula ("buckthorn" from a species name)

vombatu ("wombat")

alba'aka ("basil" from Spanish)

lujvo + fu'ivla

It is possible to absorb a fu'ivla into a lujvo, with principles varying among Lojbanists. Notable proponents are Pierre Abbat and Jorge Llambías. Here are some comparisons of their methods drawn from the Lojban mailing list (as of July 2007):

me'andi + skari
me'andyska (Abbat)
me'andi'yska (Llambías)

gurnrtefi + nanba
gurnrtefynanba (Abbat)
gurnrtefi'ynanba (Llambías)

mikri + enri
miky'enri (Abbat)
miky'enri (Llambías)

tanru

A group of two or more brivla (possibly with associated cmavo) is called tanru. They are always divisible into parts without any morphological breakage; they are a mere sequence of multiple gismu or lujvo or fu'ivla rather than a single distinctive morphological unit. See also: Syntax and semantics

cmavo

Lojban structure words, cmavo, are recognized by following properties:

• may be a single syllable
• never contain a consonant cluster of any type, whether or not y is counted
• end in a vowel
• need not be penultimately stressed, though they often are if they have more than one syllable

And they display one of the following letter patterns: V, VV, V'V, CV, CVV, CV'V. Their forms generally does not indicate anything about its grammatical function.

cmavo can be sequenced without spaces and without any change to its meaning:

pa re ci (123) = pareci (123)

se pi'o (using ...) = sepi'o (using ...)

As far as the stress rules of Lojban are concerned, such compound cmavo are still separate words, so penultimate stress (e.g. paREci) is not obligatory.

Some cmavo have rafsi, which may help converting tanru into lujvo:

ve detri --> veldetri

se ke cpacu djica --> selkemcpadji

cmene

cmene stand for things (including people) in descriptions or in direct address (cf. proper nouns). Mostly they can be in any form as long as they end in a consonant. The practice by which names in natural languages are modified to be used in Lojban is known as "lojbanization".

la bionses.nolz., (a possible realization of the name "Beyoncé Knowles")

rafsi

A special fragmentary form of gismu and cmavo, from which a new word may be created, is called rafsi. brivla such as lujvo or fu'ivla are usually derived from them (this, in turn, means that lujvo and fu'ivla have no rafsi form of their own). rafsi cannot by themselves function as an individual word; they need to be in a combined form to be used.

solri (original gismu): sol, solr, solri (assigned rafsi): solxrula (derivative lujvo)

ke (original cmavo): kem (assigned rafsi): selkemcpadji (derivative lujvo)

sampli (derivative lujvo): sam, pli (component rafsi, from skami and pilno respectively)

The unambiguity of Lojban morphology, according to John Woldemar Cowan, gives rise to "significant clues to the meaning and the origin of the word, even if you have never heard the word before". He further says: "The same principle allows you, when speaking or writing, to invent new brivla for new concepts 'on the fly'; yet it offers people that you are trying to communicate with a good chance to figure out your meaning. In this way, Lojban has a flexible vocabulary which can be expanded indefinitely."

Syntax and semantics

According to What Is Lojban?, the language's grammatical structures are "defined by a set of rules that have been tested to be unambiguous using computers", which is called the "machine grammar". Hence the characteristics of the standard syntactic (not semantic) constructs in Lojban:

• each word has exactly one grammatical interpretation;
• the words relate grammatically to each other in exactly one way.

Such standards, however, are to be attained with certain carefulness:

It is important to note that new Lojbanists will not be able to speak 'perfectly' when first learning Lojban. In fact, you may never speak perfectly in 'natural' Lojban conversation, even though you achieve fluency in the language. No English speaker always speaks textbook English in natural conversation; Lojban speakers will also make grammatical errors when talking quickly. Lojbanists will, however, be able to speak or write unambiguously if they are careful, which is difficult if not impossible with a natural language.

Nick Nicholas and John Cowan. What Is Lojban? II.3

The computer-tested, unambiguous rules also include grammar for 'incomplete' sentences e.g. for narrative, quotational, or mathematical phrases.

Lojbanic expressions are modular; smaller constructs of words are assembled into larger phrases so that all incorporating pieces manifest as a possible grammatical unity. This mechanism allows for simplistic yet infinitely powerful phrasings; "a more complex phrase can be placed inside a simple structure, which in turn can be used in another instance of the complex phrase structure".

bridi

basics

Being derived from predicate logic, the basic unit of Lojban expression is predication, a claim that some objects stand in some relationship, or that some single object has some property. bridi is the Lojban term for this type of unit. Just as a predication is formed by a predicate and arguments in formal logic, bridi are formed by selbri and sumti in Lojban. A construct of selbri and sumti produces a claim that something stands in a specified relationship to something else or has a specified property.

do | viska | le nixli
(Two sumti and one selbri, making up one bridi, claiming that a relation viska exists between do and le nixli. The selbri needs not be literally between sumti. The example can also be rendered as do le nixli viska. A more detailed discussion on Lojban word order below.)

Multiple bridi can be either sequenced across multiple sentences or compounded in one sentence:

do | melbi | .i | do | xendo
(Two sentences, each consisting of one sumti and one selbri. .i separates sentences.)

do | melbi | .ije | do | xendo
(This sentence is syntactically identical to the last one but differs in meaning. .ije may be spelled as .i je.)

do | melbi | gi'e | xendo
(One sentence, consisting of one sumti and two selbri. gi'e separates bridi as well as compounding them.)

do | melbi | gi'e | xendo | .iki'ubo | mi | nelci | do
(Two sentences, one of which includes compound bridi. While .i simply marks a division of sentences, ki'u together with bo adds that there is a particular logical connection between the first and second sentence. .iki'ubo may be spelled as .i ki'u bo.)

A compound bridi can includes multiple tenses and sumti:

mi | puze'u gunka | gi'e | ca tatpi

mi | ca'o klama | ta | ti | le karce | gi'e | ba tavla | do | la lojban.

The implicit grammatical divisions can be made explicit by separator words such as cu and vau, which are often elidable but sometimes need to be present to avoid ambiguity:

le nixli cu melbi
(This instance shows that the left-hand gismu is sumti and the right-hand gismu is selbri. Without cu the two gismu would be grammatically undistinguishable.)

mi dunda le cukta gi'e lebna lo rupnu vau do
(vau indicates that the two bridi, dunda le cukta and lebna lo rupnu, sharing the same first sumti mi, together terminate at that position, enabling them to have the subsequent do as their mutual second sumti. Compare it with its longer equivalent: mi dunda le cukta do .ije mi lebna lo rupnu do.)

The places of cu and vau in the previous examples can be rendered as follows:

do (cu) viska le nixli (vau)

do (cu) melbi (vau) .i do (cu) xendo (vau)

do (cu) melbi (vau) gi'e xendo (vau) (vau)
(The last vau marks the mutual termination of the two bridi.)

do (cu) melbi (vau) gi'e xendo (vau) (vau) .i do (cu) xendo (vau)

The ordered sets of sumti assigned to every selbri are known as "place structures". They are explicitly defined in dictionaries or word lists.

mi | tavla | do | la lojban. | le glibau
(Two sumti mi and do are fitting into the place structure of the selbri tavla, which is "x1 talks/speaks to x2 about subject x3 in language x4".)

Some lujvo formations usually operate on the place structure in predictable ways. The rafsi {gau}, for instance, inserts one place for the agent and pushes all others down one. Thus brivla can have indefinitely many places. This contrasts with the accusative alignment or ergative alignment that most languages have, in which there is a small number of named places (subject, direct object, indirect object) and all others are expressed by prepositions.

The typology of Lojban is basically Subject Verb Object, with Subject Object Verb also common. However, it can practically be anything:

mi | prami | do (SVO)

mi | do | prami (SOV)

do | se prami | mi (OVS)

do | mi | se prami (OSV)

prami | fa mi | do (VSO)

prami | fe do | fa mi (VOS)

Such flexibility has to do with the language's intended capability to translate as many expressions of natural languages as possible, based on a unique positional case system. The meaning of the sentence mi prami do is determined by prami realizing, with its own predefined place structure, a specific semantic relation between mi and do; when the positional relation between mi and do changes, the meaning of the sentence changes too. As shown above, Lojban has particular devices to preserve such semantic structure of words while altering their order. Compare the followings:

mi | tavla | do | la lojban. | le glibau ( 1 | selbri | 2 | 3 | 4 )
"x1 (mi) talks/speaks to x2 (do) about subject x3 (la lojban.) in language x4 (le glibau)"

do | se tavla | mi | fo le glibau | fi la lojban. ( 2 | selbri | 1 | 4 | 3 )
"x2 (do) is talked/spoken to by x1 (mi) in language x4 (le glibau) about subject x3 (la lojban.)"

se converts the x1 and x2 sumti place. fo tags the x4 place, and fi the x3. Such conversion and tagging is often used to emphasize particular sumti by bringing it forwards.

Here are some collations of natural languages and Lojban:

Labhraíonn Mícheál Gaeilge le Cáit (VSO - Irish)
speaks | Mícheál | Irish | with Cáit
tavla fa la mixal. fo la sicko'o fe la kat.
speaks | Mícheál | in Irish | to/with Cáit

Mamaky boky ny mpianatra (VOS - Malagasy)
reads | book | the student
tcidu lo cukta fa le tadni
reads | a book | the student

Âi ba, wa mo. (OSV - Xavante)
to the-river | I | go
fe le rirxe fa mi klama
to the river | I | go

Ihtébani o'ílaci yawi-pó=ra (OVS - Guarijio)
Esteban house-at | dance-[passive].[future]=[reportative]
ti'e bu'u le zdani be la esteban ba nu dansu
[I hear!] at the house of Esteban | [future] event-of dance

ماعِندِي قَلَمُ (SVO - Arabic)
I | not have | a pen.
mi na ponse lo penbi
I | [false] have | a pen.

僕がこれを作ったんだよ。 (SOV - Japanese)
I | this | made-[assertive-calling]
mi ti pu zbasu vau je'uju'i
I | this | [past] make [bridi-terminator] [truth-attention]

It is important to note that Lojban selbri is not a real equivalent of verb in natural languages. A selbri can be either a verb or a noun or an adjective. Its function is determined syntactically, not morphologically. An analogy to natural language word orders by using such terms as Subject, Verb, and Object does not truthfully describe the nature of Lojban bridi.

sumti

There are five kinds of simple sumti:

1. descriptions, which usually begin with a descriptor such as le;
2. pro-sumti, the Lojban analogue of pronouns, such as mi;
3. names, which usually begin with la, such as la lojban.;
4. quotations, which begin with lu/le'u/zo/zoi;
5. pure numbers, which usually begin with li.

Descriptions have the most complicated syntax and usage. Closely interwoven with this kind are names.

description

Basic descriptions in Lojban consist of two units, LE/LA descriptors and a selbri:

le zarci

Although le is quite close in meaning to English "the", it has particularly unique implications. In this example, le creates an argument which might occur in the x1 place of the belonging selbri zarci, namely a "market". le also specifies that the speaker 1) has one or more specific markets in mind (whether or not the listener knows which ones they are) and 2) is merely describing the things he/she has in mind as markets, without being committed to the truth of that description. Whereas English-speakers must differentiate between "the market" and "the markets", Lojban-speakers are not required such choice (this rule does not mean that Lojban has no way of specifying the number of markets in such a case):

le zarci cu barda
The market is big. / The markets are big.

Since the construct le + selbri merely describes something or other which the speaker choose to represent based on his/her observation, such an expression as follows is possible:

le nanmu cu ninmu
one-or-more-specific-things-which-I-describe as "men" are women

While le is specific, lo is not:

lo zarci cu barda
one-or-more-of-all-the-things-which-really are-markets is/are-big
A market is big. / Some markets are big.

lo refers generally to one or more markets, without being specific about which. Unlike le zarci, lo zarci must refer to something which actually is a market (that is, which can appear in the x1 place of a truthful bridi whose selbri is zarci). lo nanmu cu ninmu is false as there are no objects in the real world which are both men and women.

la dissociates the subsequent selbri from its normal meaning, usually making up a name (this usage should not be confused with the other usage before regular Lojbanized names). Like le descriptions, la descriptions are implicitly restricted to those the speaker has in mind:

la cribe pu finti le lisri
the-one-named "bear" [past] creates the story.
Bear wrote the story.

All descriptions implicitly terminate with ku, which can almost always be omitted with no danger of ambiguity. The main exceptions are a) when relative clauses are involved and b) when a description immediately precedes the selbri (in which case using an explicit cu before the selbri makes the ku unnecessary). Other usages of ku include making a compound negator (naku) and terminating place-structure/tense/modal tags (puku, baiku).

selbri

tanru

Multiple brivla may be linked up together so as to more specifically conceptualize the intended meaning. The tanru in lo skami pilno "computer user(s)", the modifying brivla skami narrows the sense of the modified brivla pilno to form a more specific concept (in which case the modifier may resemble English adverbs or adjectives). Without skami, lo pilno will just mean "user". Other examples:

ti mutce xamgu ("This is very funny.")

do melbi se kanla ("You have beautiful eye(s).")

.ue.oi le mabla bebna cu zvati ti ("Oh my gosh the damn idiot is here.")

cmavo

connectives

As befits a logical language, there is a large assortment of conjunctions.

There exist 16 possible different truth functions, the four fundamental ones of which are assigned four vowels in Lojban. These vowels are a component sound from which actual logical-connective cmavo are built up.

A	FIRST is true and/or SECOND is true (TTTF)
E	FIRST is true and SECOND is true (TFFF)
O	FIRST is true if and only if SECOND is true (TFFT)
U	FIRST is true whether or not SECOND is true (TTFF)

With the four vowels, the ability to negate either sentence, and the ability to exchange the sentences, as if their order had been reversed, Lojban can create all of the 16 possible truth functions except TTTT and FFFF (which are fairly useless anyway). In order to remain unambiguous, each place in the grammar of the language where logical connection is permitted has its appropriate set of connectives. If the connective suitable for sumti were used to connect selbri, ambiguity would result. Here are examples of connectives suitable for sumti:

la djekl. .a la xaid. zvati ti
Jekyll and/or Hyde is/are here.

la djekl. .e la xaid. zvati ti
Jekyll and Hyde is here.

la djekl. .o la xaid. zvati ti
Jekyll if-and-only-if Hyde is here.

la djekl. .u la xaid. zvati ti
Jekyll whether-or-not Hyde is here.

Variations of these truth functions can be made as follows:

la djekl. na.a la xaid. zvati ti
Jekyll only-if Hyde is here.

la djekl. .enai la xaid. zvati ti
Jekyll and-not Hyde is here.

la djekl. .onai la xaid. zvati ti
Jekyll either/or Hyde is here.

Connections between components other than sumti can be expressed as follows (note that their functions are in accordance with the assigned vowels):

la djekl. tavla .ija la xaid. tavla (between sentences)
Jekyll speaks. And/or Hyde speaks.

la djekl. mikce la xaid. gi'e nanmu (between bridi)
Jekyll is a doctor of Hyde and is a man.

la djekl. sipna je cadzu (between gismu)
Jekyll sleeps-and-walks."

Connections can be questioned:

la djekl. ji la xaid. tavla
Jekyll [what?] Hyde speaks.

la djekl. sipna je'i cadzu
Jekyll sleeps [what?] walks.

attitudinals

Attitudinals are a set of cmavo which allow the speakers to express their emotional state or source of knowledge, or the present stage of discourse. In natural languages, attitudes are usually expressed by the tone of voice when speaking, and (very imperfectly) by punctuation when writing; in Lojban, such information are extensively expressible in words. And the meanings are to be understood separately from the main predicate.

.iu (love)

.ui (happy)

They may be "scaled" by suffixes:

.uinai (happy-not = unhappy)

.uicai (happy-intense = very very happy)

.uicu'i (happy-neutral)

Combination is possible, and highly productive as well as creative:

.uinaicai (happy-not-intense)

.iu.uinai (love-happy-not = I am unhappily in love)

Evidentials, derived from those of American Indian languages and the constructed language Láadan, show how the speaker came to say the utterance, i.e. the source of the information or the idea:

ti'e la .uengas cu zergau
[I hear!] Wenga is-a-criminal-doer.
I hear that Wenga is a crook.

ba'acu'i le tuple be mi cu se cortu
[I experience!] The leg of me is-the-locus-of-pain.
My leg hurts.

pe'i la kartagos. .ei se daspo
[I opine!] Carthage [obligation] is-destroyed.
In my opinion, Carthage should be destroyed.

prepositions

There are two kinds of prepositions (sumtcita, which refers to adpositions in general) in Lojban: tense markers and proper prepositions. The syntactic difference is that a proper preposition can be converted with se, whereas a tense marker cannot. All proper prepositions (except the vague one do'e) are formed from a brivla and mark their object semantically as being in a place of that brivla. Thus the following are equivalent:

mi pilno lo me'andi lo nu skagau lei kerfa
I use henna to color the hair.

mi skagau lei kerfa sepi'o lo me'andi
I color the hair with henna.

Prepositions (including tense markers) can also be placed in .i ... bo to make sentence conjunctions. With most prepositions this makes no sense, but ki'u, ja'e, mu'i and ni'i are often used this way to express various kinds of "because" and "therefore":

la djan. cpacu le pamoi se jinga .iki'ubo ri jinga
John got the first prize because he won.

tenses

Lojban has unique 63 tense words to express various aspects of both space and time as well as event (such a system is unusual among other languages in that it deals with spatial and temporal aspects in the same term). They can be roughly subdivided as follows:

• intervals: pu, ca, ba, bu'u, ri'u, ni'a ...
• modifiers: ze'i, zi, ve'i, vi ...
• contours: co'a, pu'o, de'a ...
• converters: fe'e, roi, mo'i ...

Marking tenses is always optional in Lojban:

mi klama le zarci (default: no temporal tense)
I went/have-gone/go/am-going/will-go/continually-go-to the-market.

mi ba'o klama le zarci
I have-gone-to the-market.

mi capu'o klama le zarci
I am-about-going-to the-market.

Where the tense information is not specified, the context resolves the interpretation.

Tense words are usually put right before the selbri:

mi [cu] pu klama le zarci (cu is the implicit separator between the first sumti mi and the selbri klama.)

They may be placed elsewhere with the additional terminator ku:

pu ku mi [cu] klama le zarci

mi [cu] klama pu ku le zarci

mi [cu] klama le zarci pu [ku] (ku is elidable at the end of the bridi)

The terminator is used so that the tense word do not directly run into the following sumti and modify it. Compare the next sentences:

baku le nunsalci cu cfari
[At some point in the future] the festival will start.

ba le nunsalci cu cfari
After the festival, [something unspecified] will start.

Tenses can be "layered up":

mi pu klama le zdani .i le zdani pupu se daspo
I [past] go-to the house. The house [past][past] be-destroyed.
I went to the house. The house had been destroyed.

Tenses can be "sticky" by being set with ki, continuing in effect over more than a single bridi, until it is unset:

mi puki fengu binxo .i le nixli cu klaku cfari .i mi ki xenru
I [past]-[set this tense] angry-kind-of become. The girl crying-kind-of start. I [set this tense] regret.
(Earlier) I got angry. The girl started crying. (Now) I regret.

The second ki resets the tense to the implicit default time from the speaker's point of view, which is "now" (this means that ki may be used as a tense word by itself).

Using ki, equivalents of the previous layering tenses can be produced:

mi puki klama le zdani .i le zdani pu se daspo

The second pu is to be counted from the tense set by the last ki, so in effect it is equivalent to pupu.