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Morphology and word classes

Okay, we covered a lot of ground so far. We mostly did that by focusing on immediately useful Lojbanic constructs for everyday usage, and then applying those constructs in exercises. This lesson will be a bit different. Instead of focusing on a single construct, we will cover the basics of Lojban morphology, as this knowledge will help you learn many other concepts down the road.

What is morphology? The word is derived from Greek meaning the study of shapes, and in this context, it refers to how we make words from letters and sounds, as contrasted with syntax – how we make sentences with words. Lojban operates with different morphological word classes, which are all defined by their morphology. To make it all nice and systematic, words with certain functions tend to be grouped by morphological classes, though exceptions may occur.

Class Meaning Defined By Typical Function
brivla Bridi-word. Among first 5 letters (excluding ' ) is a consonant cluster. Ends in vowel. Acts as a selbri by default. Always has a place structure.
\___ gismu Root-word. 5 letters of the form CVCCV or CCVCV. One to five sumti places. Covers (arbitrarily chosen) basic concepts.
\___ lujvo Compound word. Derived from from lujvla, meaning complex word. Min. 6 letters. Made by stringing rafsi together with binding letters if necessary. Covers more concepts than gismu.
\___ zi'evla Free-word. As brivla, but do not meet defining criteria of gismu or lujvo, ex: angeli (angel). Covers unique concepts like names of places or organisms.
cmevla Name-word. Beginning and ending with pause (full stop). Last sound/letter is a consonant. Always acts as a name or as the content of a quote.
cmavo Grammar-word. From cmavla, meaning small word. One consonant or zero, always at the beginning. Ends in a vowel. Grammatical functions. Varies.
Word fragments:
rafsi Affix. CCV, CVC, CV'V, -CVCCV, -CCVCV, CVCCy- or CCVCy-. Not actual words, but can be stringed together to form lujvo.

Let's go through each word class:

  • cmevla are very easy to identify because they begin and end with a pause, signaled by a full stop in writing, and the last letter is a consonant. Cmevla have two functions: they can either act as a proper name, if prefixed by the article la (explained in next lesson); or they can act as the content of a quote. One can mark stress in the names by capitalizing the letters which are stressed. Examples of cmevla are: .io'AN. (Johan), .mat. (Matt), .djan. (John) and .cumindzyn. (Xuming Zeng). Names which do not end in consonants need to have one added: .anas. (Anna); or removed: .an..
  • brivla are called bridi-words because they by default are selbri, and therefore almost all Lojban words with a place structure are brivla. This has also given them the English nickname content-words. It's nearly impossible to say anything useful without brivla, and almost all words for concepts outside lojban grammar (and even most of the words for things in the language) are captured by brivla. As shown in the table, brivla has three subcategories:
    • gismu are the root words of the language. Only about 1450 exist, and very few new ones are added. They cover the most basic concepts like circle, friend, tree and dream. Examples include prenu, pelxu and dunda.
    • lujvo are made by combining rafsi (see under rafsi), to cover more concepts than gismu alone. By combining rafsi, one narrows down the meaning of the word. Lujvo are made by an elaborate algorithm, so making valid lujvo on the fly is near impossible, with few exceptions like selpa'i, from se prami, which can only have one definition. Instead, lujvo are made once, its place structure defined, and then that definition is made official by the dictionary. Examples include brivla (bridi-word), jbobau (lojbanic-language = Lojban) and cakcinki (shell-insect = beetle).
    • zi'evla are made by making up words which fit the definition for brivla, but not for lujvo or gismu. They tend to cover concepts which are hard to cover by lujvo, for instance names of species, nations or very culture-specific concepts. Examples include xanguke (South Korea), cidjrpitsa (pizza) and .angeli (angel).
  • cmavo are small words with one or zero consonants. They tend to not signify anything in the exterior world, but to have only grammatical function. Exceptions occur, and it's debatable how much attitudinals exists for their grammatical function. Another weird example are the words of the class GOhA, which act as brivla. It is valid to type several cmavo in a row as one word, as we previously mentioned. By grouping certain cmavo in functional units, though, it is sometimes easier to read. Thus, uipuzuvukumi citka is valid, and is parsed and understood as ui pu zu vu ku mi citka. Like other Lojban words, one should (but need not always) place a full stop before any words beginning with a vowel.
    • cmavo of the form xVV, CV'VV or V'VV are experimental, and are words which are not in the official language definition, but which have been added by Lojban users to respond to a certain need.
  • rafsi are not Lojban words, and can never appear alone. However, several (more than one) rafsi combine to form lujvo. These must still live up to the brivla-definition, for instance "lojban" is invalid because it ends in a consonant (which makes it a cmevla), and "ci'ekei" is invalid because it does not contain a consonant cluster, and is thus read as two cmavo written as one word. Often, a 3-4 letter string is both a cmavo and a rafsi, like mu'i, which is both the BAI and the rafsi for mukti. Note that there is nowhere that both a cmavo and a rafsi would be grammatical, so these are not considered homophones. All gismu can double as (word-final) rafsi, if they are prefixed with another rafsi. The first four letter of a gismu suffixed with an "y" can also act as a rafsi, if they are suffixed with another rafsi. The vowel "y" can only appear in lujvo or cmevla. Valid rafsi letter combinations are: CVV, CV'V, CCV, CVCCy- CCVCy-, -CVCCV and -CCVCV.

Mind map

While studying, you may find the following mind map useful:

Mind map of Lojban grammar

We recommend bookmarking it.


Now, try to infer the classification of a few words you are already familiar with:

Word Class
mi cmavo
dunda brivla (more specifically, gismu)
.djan. cmevla
sedu'u two words: se (cmavo) + du'u (cmavo)
gau cmavo (also rafsi for gasnu)
melbi brivla (more specifically, gismu)
sepi'o two words: se (cmavo) + pi'o (cmavo, and also rafsi for pilno)
kei cmavo


As usual, before proceeding to the next lesson, get some practice with interactive exercises – look for the "Practice" button nearby!

Beware that exercises loop indefinitely, so feel free to stop once you feel you've had enough. And be sure to revisit exercises on different days, to benefit from the spacing effect.

Lesson plan

  • Lesson
    • Cover basic word classes
  • New exercises
    • Categorize word between cmevla, brivla and cmavo (OK)
    • Identify the glosses of brivla, gismu, lujvo, zi'evla, cmevla, cmavo (OK)


dunda x1 [donor] gives/donates gift/present x2 to recipient/beneficiary x3 [without payment/exchange]

pelxu x1 is yellow/golden [color adjective]

zdani x1 is a nest/house/lair/den/[home] of/for x2

tavla x1 talks/speaks to x2 about subject x3 in language x4

pendo x1 is/acts as a friend of/to x2 (experiencer); x2 befriends x1

prenu x1 is a person/people (noun) [not necessarily human]; x1 displays personality/a persona

mlatu x1 is a cat/[puss/pussy/kitten] [feline animal] of species/breed x2; (adjective:) x1 is feline

ctuca x1 teaches audience x2 ideas/methods/lore x3 (du'u) about subject(s) x4 by method x5 (event)

nelci x1 is fond of/likes/has a taste for x2 (object/state)

gerku x1 is a dog/canine/[bitch] of species/breed x2

melbi x1 is beautiful/pleasant to x2 in aspect x3 (ka) by aesthetic standard x4

sutra x1 is fast/swift/quick/hastes/rapid at doing/being/bringing about x2 (event/state)

lojbo x1 reflects [Loglandic]/Lojbanic language/culture/nationality/community in aspect x2

ciska x1 inscribes/writes x2 on display/storage medium x3 with writing implement x4; x1 is a scribe

djuno x1 knows fact(s) x2 (du'u) about subject x3 by epistemology x4

nupre x1 (agent) promises/commits/assures/threatens x2 (event/state) to x3 [beneficiary/victim]

cusku x1 (agent) expresses/says x2 (sedu'u/text/lu'e concept) for audience x3 via expressive medium x4

gleki x1 is happy/gay/merry/glad/gleeful about x2 (event/state)

citka x1 eats/ingests/consumes (transitive verb) x2

plise x1 is an apple [fruit] of species/strain x2

vecnu x1 [seller] sells/vends x2 [goods/service/commodity] to buyer x3 for amount/cost/expense x4

skami x1 is a computer for purpose x2

pilno x1 uses/employs x2 [tool, apparatus, machine, agent, acting entity, material] for purpose x3

cmene x1 (quoted word(s)) is a/the name/title/tag of x2 to/used-by namer/name-user x3 (person)

bangu x1 is a/the language/dialect used by x2 to express/communicate x3 (si'o/du'u, not quote)

fanva x1 translates text/utterance x2 to language x3 from language x4 with translation result x5

mukti x1 (action/event/state) motivates/is a motive/incentive for action/event x2, per volition of x3

gasnu x1 [person/agent] is an agentive cause of event x2; x1 does/brings about x2

lerci x1 (event) is late by standard x2


mi pro-sumti: me/we the speaker(s)/author(s); identified by self-vocative

do pro-sumti: you listener(s); identified by vocative

ti pro-sumti: this here; immediate demonstrative it; indicated thing/place near speaker

ta pro-sumti: that there; nearby demonstrative it; indicated thing/place near listener

zo'e pro-sumti: an elliptical/unspecified value; has some value which makes bridi true

lo veridical descriptor: the one(s) that really is(are) ...

ku elidable terminator: end description, modal, or negator sumti; often elidable

fa sumti place tag: tag 1st sumti place

fe sumti place tag: tag 2nd sumti place

fi sumti place tag: tag 3rd sumti place

fo sumti place tag: tag 4th sumti place

fu sumti place tag: tag 5th sumti place

se 2nd conversion; switch 1st/2nd places

te 3rd conversion; switch 1st/3rd places

ve 4th conversion; switch 1st/4th places

xe 5th conversion; switch 1st/5th places

xu discursive: true-false question

ma pro-sumti: sumti question (what/who/how/why/etc.); appropriately fill in sumti blank

mo pro-bridi: bridi/selbri/brivla question

na bridi contradictory negator; scope is an entire bridi; logically negates in some cmavo compounds

go'i pro-bridi: preceding bridi; in answer to a yes/no question, repeats the claim, meaning yes

su'u abstractor: generalized abstractor (how); x1 is [bridi] as a non-specific abstraction of type x2

nu abstractor: generalized event abstractor; x1 is state/process/achievement/activity of [bridi]

du'u abstractor: predication/bridi abstractor; x1 is predication [bridi] expressed in sentence x2

sedu'u compound abstractor: sentence/equation abstract; x1 is text expressing [bridi] which is x2

kei elidable terminator: end abstraction bridi (often elidable)

vau elidable: end of sumti in simple bridi; in compound bridi, separates common trailing sumti

cu elidable marker: separates selbri from preceding sumti, allows preceding terminator elision

poi restrictive relative clause; attaches subordinate bridi with identifying information to a sumti

noi non-restrictive relative clause; attaches subordinate bridi with incidental information

ke'a pro-sumti: relativized sumti (object of relative clause)

ku'o elidable terminator: end NOI relative clause; always elidable, but preferred in complex clauses

be sumti link to attach sumti (default x2) to a selbri; used in descriptions

bei separates multiple linked sumti within a selbri; used in descriptions

be'o elidable terminator: end linked sumti in specified description

pi'o pilno modal, 1st place used by ...

mu'i mukti modal, 1st place because of motive ...

gau gasnu modal, 1st place agent/actor case tag with active agent ...

pu time tense relation/direction: did [selbri]; before/prior to [sumti]; default past tense

ca time tense relation/direction: is [selbri]; during/simultaneous with [sumti]; present tense

ba time tense relation/direction: will [selbri]; after [sumti]; default future tense

zo quote next word only; quotes a single Lojban word (not a cmavo compound or tanru)

lu start grammatical quotation; quoted text should be grammatical on its own

li'u elidable terminator: end grammatical quotation; seldom elidable except at end of text

ne non-restrictive relative phrase marker: which incidentally is associated with ...

pe restrictive relative phrase marker: which is associated with ...; loosest associative/possessive

po restrictive relative phrase marker: which is specific to ...; normal possessive physical/legal

po'e restrictive relative phrase marker: which belongs to ... ; inalienable possession

.a logical connective: sumti afterthought or

.e logical connective: sumti afterthought and

.o logical connective: sumti afterthought biconditional/iff/if-and-only-if

.u logical connective: sumti afterthought whether-or-not

na'e contrary scalar negator: other than ...; not ...; a scale or set is implied

to'e polar opposite scalar negator

no'e midpoint scalar negator: neutral point between je'a and to'e; "not really"

tu'a extracts a concrete sumti from an unspecified abstraction; equivalent to le nu/su'u [sumti] co'e

jai convert tense/modal (tagged) place to 1st place; 1st place moves to extra FA place (fai)


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