Lojban uses three kinds of words:
Names, or cmene, are very much like their counterparts in other languages. They are labels applied to things or people, to stand for them in descriptions or in direct address. They may convey meaning in themselves, describing concretely what they are refering to, but do not necessarily do so. Because names are often highly personal and individual, Lojban attempts to allow native language names to be used with a minimum of modification. However, most names must be Lojbanized to some extent, to prevent potential ambiguities. Examples of Lojbanized cmene include:
cmene may have almost any form, but always end in a consonant, and are followed by a pause. cmene are penultimately stressed, unless unusual stress is marked with capitalization. A cmene may have multiple parts, each ending with a consonant and pause, or the parts may be combined into a single word with no pause. Thus djan. djonz. /jahn.jonz./ and djandjonz. /JAHNjonz./ are valid (American) Lojbanizations of John Jones, while .iunaited. steits. and either .iuNAItet,steits. or .iunaitet,STEITS. are valid Lojbanizations for United States, depending on how you wish to stress the name. In the last example, writing the cmene as a single word requires capitalization of the stressed syllables /NAI/ or /STEITS/, neither of which is penultimate in the single-word form of the cmene.
Note: Lojban words do not allow a voiced consonant (like d) to be next to an unvoiced consonant (like s), without an intervening pause. This is why the single-word version of United States goes into Lojban as .iunaitet,steits., whereas the two-word version remains as is: .iunaited.steits.
The final arbiter of the correct form of the cmene is the person doing the naming -- although most cultures grant people the right to determine how they want their own name to be spelled and pronounced. The English Mary can thus be Lojbanized as meris., maris., meiris., or even marys. The latter is not pronounced much like its English equivalent, but may be desirable to someone who values spelling over pronunciation consistency. The final letter need not be an s; it must, however, be a Lojban consonant of some variety.
cmene are not permitted to have the words la, lai, or doi embedded in them, because they are always preceded by one of these words or by a pause. With one of these words embedded, the cmene might break up into valid Lojban words followed by a shorter, incorrect cmene. There are similar alternatives to these that can be used in Lojbanization, such as ly, lei, and do'i, that do not cause these problems.
'Predicate' words, or brivla, are the core of Lojban. The concept of 'predicate', or bridi, will be discussed in the grammar section below. brivla carry most of the semantic information in the language. They serve as the equivalent of English nouns, verbs, adjectives, and adverbs, but are treated identically in Lojban grammar.
brivla may be recognized by several properties:
they have more than one syllable
they end in a vowel
The consonant cluster rule has the qualification that the letter y is totally ignored, even if it splits a consonant cluster. Thus lobypei /LOBE,uh,pay/ is a brivla even though the y separates the bp cluster.
brivla are divided into three subcategories according to how they are created:
the 'primitive' roots of Lojban; e.g. klama
compounds of gismu, or their abbreviations, with meanings defined from their components; e.g. lobypli
'borrowings' from other languages that have been Lojbanized (in a manner similar to how cmene are Lojbanized) in order to fit within the brivla requirements; e.g. cidjrspageti 'spaghetti' (it's not nearly as hard to say as it looks!)
brivla are defined so as to have only one meaning, which is expressed through a unique place structure. This concept is discussed further in the sections on semantics and grammar.
occurrence or word frequency in other languages
usefulness in building complex concepts
and a few, like the words gismu, cmavo, and lujvo, are included as uniquely Lojbanic concepts that are basic to the language.
Each gismu is exactly five letters long, and has one of two consonant-vowel patterns: CVCCV or CCVCV (e.g. rafsi, bridi). The gismu are built so as to minimize listening errors in a noisy environment.
When specifying a concept that is not found among the gismu, a Lojbanist generally attempts to express the concept as a tanru. tanru is an elaboration of the concept of 'metaphor' used in English. In Lojban, any brivla can be used to modify another brivla. The first of the pair modifies the second. Modifier brivla may thus be regarded as acting like English adverbs or adjectives. For example, skami pilno is the tanru which expresses the concept of 'computer user'.
When a concept expressed in a tanru proves useful, or is frequently expressed, it is desirable to choose one of the possible meanings of the tanru and assign it to a new, single brivla. In the example, we would probably choose the meaning 'user of computers', and form the single brivla sampli, out of the tanru skami pilno. Such a brivla, built from two or more component gismu, is called a lujvo.
Like gismu, however, lujvo have only one meaning. Unlike gismu, lujvo may have more than one form. This is because each gismu has between two and five combining forms called rafsi, which are joined together in order to form a lujvo (e.g. sam and skam for skami; pli and piln for pilno). Longer rafsi may be used in place of shorter rafsi; the result is considered the same lujvo, even though the word is spelled and pronounced differently. Thus brivla, itself a lujvo built from the tanru bridi valsi, is the same lujvo as brivalsi, bridyvla, and bridyvalsi -- each using a different combination of rafsi.
The use of tanru or lujvo is not always appropriate for very concrete or specific terms (e.g. brie or cobra), or for jargon words specialized to a narrow field (e.g. quark, integral, or iambic pentameter). These words are in effect 'names' for concepts, and the names were invented by speakers of another language. The vast majority of names for plants, animals, foods, and scientific terminology cannot be easily expressed as tanru. They thus must be 'borrowed' (actually 'copied') into Lojban from the original language, forming words called fu'ivla.
A borrowed word must be Lojbanized into one of several permitted fu'ivla forms. A rafsi is then attached to the beginning of the Lojbanized form, usually using a syllabic consonant as 'glue' to ensure that the resulting word is not construed as two separate words. The rafsi categorizes or limits the meaning of the fu'ivla; otherwise a word having several different jargon meanings in other languages (such as integral) would be unclear as to which meaning should be assigned to the fu'ivla. fu'ivla, like other brivla, are not permitted to have more than one definition.
cmavo are the structure words that hold the Lojban language together. They often have no concrete meaning in themselves, though they may affect the semantics of brivla to which they are attached. cmavo include the equivalent of English articles, conjunctions, prepositions, numbers, and punctuation marks.
cmavo are recognized most easily by not being either cmene or brivla. Thus, they:
may be a single syllable
end in a vowel
need not be penultimately stressed, though they often are if they have more than one syllable
All cmavo display one of the following letter patterns, where C stands for a consonant, and V stands for a vowel:
The letter pattern generally does not indicate anything about the grammar of the cmavo.
A sequence of cmavo can be written without intervening spaces, without any change to its meaning. Such a sequence is called a compound cmavo. For example, a set of digits comprising a longer number can be written as a single word (e.g. pareci = pa + re + ci = '123').
Note: As far as the stress rules of Lojban are concerned, however, these are still separate words. So you don't have to stress pareci as paREci.