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Lojban logo

The artificial language Lojban (IPA , official full name Lojban: a realization of Loglan) was created by the Logical Language Group in 1987 based on the earlier Loglan, with the intent to make the language more complete, usable, and freely available. It has the ISO 639 language code jbo.

The language itself shares many of the features and goals of Loglan; in particular

  • The grammar is based on predicate logic, and is capable of expressing complex logical constructs precisely.
  • It has no irregularities or ambiguities in spelling or grammar, so it can be easily parsed by computer.
  • Lojban is designed to be as culturally neutral as possible.
  • It is, nonetheless, simple to learn and use compared to many natural languages.

While the initial goal of the Loglan project was to investigate the Sapir-Whorf Hypothesis, the active Lojban community has additional goals for the language, including

  • General research into linguistics
  • Research in artificial intelligence and machine understanding
  • Improved human-computer communication, storage ontologies, and computer translation of natural language text
  • Use of language as an educational tool
  • Personal creativity

Like most languages with few speakers, Lojban lacks an associated body of literature.



The Lojban alphabet consists of the 26 characters ' , . a b c d e f g i j k l m n o p r s t u v x y z; that is, it consists of the Latin alphabet without the three letters h q w but with three additional letters. The alphabetical order is as shown above, which is (intentionally) the same as the sort order of those characters in ASCII.

Capital letters are also used, but only to mark a stressed syllable in a word when the stress is on a non-standard syllable (for example, in proper names). Capital letters are not considered separate letters of the alphabet. It is optional whether only the stressed vowel or the entire stressed syllable is capitalised; for example, the name "Josephine" could be rendered as either DJOzefin. or djOzefin. Without the capitalisation, the ordinary rules of Lojban stress would cause the 'ze' syllable to be stressed.

Some of the letters have multiple permitted realisations. Note in particular that Lojban vowels can be either rounded or unrounded. Typical realisations are given in the following table:

Letter IPA Description
'an unvoiced glottal or dental fricative
,---the syllable separator
.a glottal stop or a pause
aan open vowel
ba voiced bilabial stop
can unvoiced coronal sibilant
da voiced dental/alveolar stop
ea front mid vowel
fan unvoiced labial fricative
ga voiced velar stop
ia front close vowel
ja voiced coronal sibilant
kan unvoiced velar stop
la voiced lateral approximant (may be syllabic)
ma voiced bilabial nasal (may be syllabic)
na voiced dental or velar nasal (may be syllabic)
oa back mid vowel
pan unvoiced bilabial stop
ra rhotic sound
san unvoiced alveolar sibilant
tan unvoiced dental/alveolar stop
ua back close vowel
va voiced labial fricative
xan unvoiced velar fricative
ya central mid vowel
za voiced alveolar sibilant

Two frequent combinations are the affricates tc and dj , which represent one sound (phoneme) each in English but are considered a combination of two phonemes in Lojban.

Lojban grammar

Lojban has three parts of speech: one (called brivla) for both common nouns and verbs, one (called cmene) for proper nouns, and another (called cmavo) for structural particles: articles, numerals, tense indicators and other such modifiers. The cmavo are further subdivided into selma'o, which are closer to the notion of parts of speech (e.g. UI includes interjections and discursives). There are no adjectives or adverbs in the sense that Indo-European languages have them. The articles inflect to indicate individual, mass, set, or typical element. Brivla do not inflect for tense, person, or number; tense is indicated by separate cmavo, but grammatical number is absent. All brivla, except for a handful of borrowings such as alga, have at least five letters.

As befits a logical language, there is a large assortment of conjunctions. Logical conjunctions take different forms depending on whether they connect sumti (the equivalent of noun phrases), selbri (phrases that can serve as verbs; all brivla are selbri), parts of a tanru (a construct whose closest English equivalent is a string of nouns), or clauses in a sentence.

The typology is Subject Verb Object, with Subject Object Verb also common. Word formation is synthetic; many basic five-letter brivla (called gismu) have one to three three-letter forms called rafsi which are used in making longer brivla. For example, gasnu means "to make something happen"; its rafsi -gau regularly forms compounds meaning "to cause...x", in which the agent is in the subject place of the new predicate.

Lojban has a positional case system, though this can be overridden by marking predicate arguments with explicit modal particles. For instance bramau means "is bigger than"; the bigger thing is in first position, and the smaller is second, and the measured property in the third (see also postfix notation). So mi bramau do le ka clani means "I am bigger than you in the property of height" or "I am taller than you"; but this could also be expressed as something like fi le ka clani fe do fa mi bramau, "In height, you are exceeded by me".

  • le cinfo cu bramau le mlatu = "The lion is bigger than the cat"
  • mi bramaugau le cinfo le mlatu = "I make the lion bigger than the cat"

What a particular place means depends entirely on the brivla. For animals and plants the second place is the species, variety, breed, or other taxon; for verbs of measurement it is the numerical measurement, and a further place is the standard; for klama ("go"/"come") it is the destination.

Something of the flavor of Lojban (and Loglan) can be imparted by this lightbulb joke:

Q: How many Lojbanists does it take to change a broken light bulb?
A: Two: one to decide what to change it into, and one to figure out what kind of bulb emits broken light.

This joke makes use of two features of the language; first, the language attempts to eliminate polysemy; that is, having a phrase with more than one meaning. So while the English word "change" can mean "to transform into a different state", or "to replace", or even "small-denomination currency", Lojban has different words for each. In particular, the use of a brivla such as the word for "change" ("binxo") implies that all of its predicate places exist, so there must be something for it to change into. Another feature of the language is that it has no grammatical ambiguities that appear in English phrases like "big dog house", which can mean either a big house for dogs or a house of big dogs. In Lojban, unless you clearly specify otherwise with cmavo, such modifiers always group left-to-right, so "big dog house" is a house of big dogs, and a "broken light bulb" is a bulb that emits broken light (you can achieve the desired meaning with the appropriate cmavo or by creating a new word, in effect saying "broken lightbulb").

Lojban compared to the Loglan of TLI

Note, Loglan is now a generic term that refers both to James Cooke Brown's Loglan, and all languages descended from it. Since the organization that Dr. Brown established, The Loglan Institute (TLI), still calls its language Loglan, it is necessary to state that we in this section are referring to the TLI language, instead of the entire family of languages.

The principal difference between Lojban and Loglan is one of lexicon. A Washington DC splinter group, which later formed The Logical Language Group, LLG, decided in 1986 to remake the entire vocabulary of Loglan in order to evade Dr. Brown's claim of copyright to the language. After a lengthy battle in court, his claim to copyright was ruled invalid. By then, though, the new vocabulary was already cemented as a part of the new language, which was called Lojban: A realization of Loglan by its supporters.

The closed set of five-letter words were the first part of the vocabulary to be remade. The words for Lojban were made by the same principles as those for Loglan; that is, candidate forms were chosen according to how many sounds they had in common with their equivalent in some of the most common spoken languages on Earth, which was then multiplied with the number of speakers of the languages with which the words had letters in common. The difference with the Lojban remake of the root words was that the weighting was updated to reflect more recent numbers of speakers for the languages. This resulted in word forms that had fewer sounds taken from English, and more sounds taken from Chinese. For instance, the Loglan word norma is equivalent to the Lojban word cnano, both meaning "normal".

Grammatical words were gradually added to Lojban as the grammatical description of the language was made.

Loglan and Lojban still have essentially the same grammars, and most of what is said in the typology section above holds true for Loglan as well. Most simple, declarative sentences could be translated word by word between the two languages; however, the grammars differ in the details, and in their formal foundations. The grammar of Lojban is defined mostly in the language definition formalism YACC, with a few formal "pre-processing" rules. Loglan also has a machine grammar, but it is not definitive; the grammar of Loglan is based on a relatively small corpus of sentences that has remained unchanged through the decades, which takes precedence in case of a discrepancy.

There are also many differences between the terminology used in English to talk about the two languages. In his writings, James Cooke Brown used many terms based on English, Latin and Greek, some of which were already established with a slightly different meaning. The Lojban camp, on the other hand, freely borrowed grammatical terms from Lojban itself. Thus, for what linguists would call roots or root words, loglanists say primitives or prims, and lojbanists say gismu. The lexeme of Loglan and selma'o of Lojban has nothing to do with the linguistic meaning of lexeme. It is really a kind of part of speech, a subdivision of the set of grammatical words, or particles, which by loglanists are called little words and by lojbanists cmavo. There is a grammatical construct in Loglan and Lojban that is called, respectively, metaphor and tanru; this is not really a metaphor per se, but a kind of modifier-modificand relationship of which a noun-noun construction is an example. A borrowed word in Loglan is simply called a borrowing; in English discussions of Lojban, the Lojban word fu'ivla is used. This is probably because in Lojban, unlike Loglan, a certain set of CV templates is reserved for borrowed words.

In the new phonology for Lojban, the consonant q and the vowel w were removed, and the consonant h was replaced by x. The consonant ' (apostrophe) was added with the value of [h] in the International Phonetic Alphabet, but its distribution is such that it can appear only intervocally, and in discussions of the morphology and phonotactics, it is described not as a proper consonant, but a "voiceless glide". (This phoneme is realized as [θ] by some speakers.) A rigid phonotactical system was made for Lojban, but Loglan does not seem to have had such a system.

The Lojban logo

The Lojban logo is the result of a poll of the members of the LLG, and is defined as a Cartesian coordinate system superimposed on a Venn diagram. This definition does not mention color, but it is traditionally reproduced with the coordinate system in red and the Venn diagram in blue.

While no official explanation of its symbolism exists, one might reasonably suppose that the Venn diagram stands for predicate logic, while the coordinate system represents rationality, mathematics and the natural sciences.

Natural Language Processing Applications

Researchers in the natural language processing field of artificial intelligence often get bogged down in aspects of natural language which are not directly relevant to their research, for example syntactic ambiguity and word sense disambiguation. To help this problem, some linguists and artificial intelligence researchers have proposed using an artificial language like Lojban, that is capable of expressing all the nuance and subtlety of the natural languages we are familiar with, but would have mathematically inviolate grammar and spelling rules, to remove all possible confusion about what a sentence is trying to say, even if it were nonsense words.

External links and references

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