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So far we have only expressed single sentences one at a time. To express more complex things, however, you often need subordinate sentences. Luckily, these are much easier in Lojban than what one would expect.

We will begin with an example to demonstrate this:

I am happy that you are my friend.

Here, the main bridi is "I am happy that X" and the sub-bridi is "you are my friend". Let's look at the definition for the word "happy" in Lojban:

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

Notice that the second place of gleki can either be an event or a state. This is natural, because one cannot be happy about an object in itself, only about some state the object is in. But alas! Only bridi can express a state or an event, and only sumti can fill the x2 of gleki!

As you might have guessed, there is a solution. The construct su'u...kei has the function of converting bridi into selbri (similarly to how lo...ku converts selbri into sumti).

su'u generalized abstractor – x1 is <BRIDI> as a non-specific abstraction of type x2.

kei end abstraction.

So "X su'u do pendo mi kei" would mean "X is (a non-specific abstraction of) you being my friend". It's usually hard to find good uses of a bridi directly as a selbri. However, since "su'u <BRIDI> kei" is a selbri, one can convert it to a sumti using lo...ku, yielding "lo su'u <BRIDI> kei ku":

mi gleki lo su'u do pendo mi kei ku
I am happy that you are my friend.
mi djuno lo su'u do nelci lo mlatu ku kei ku
I know that you like cats.
do ctuca mi lo su'u lo mlatu ku melbi kei ku
You taught me that cats are beautiful.

Specialized abstractors

In practice, su'u...kei does not see much use. Since su'u...kei is a general abstractor, it will work in all cases – but be careful: if context is not sufficiently clear, the listener may have trouble figuring out precisely what you mean. There are a variety of specialized abstractors, each conveying a specific, more precise meaning than su'u..kei. The two most popular ones are nu...kei and du'u...kei. There are many others, but we will only focus on these two for now.

nu: event/state abstractor

The construct nu...kei treats the bridi in between as an event or state, i.e. something which happens or could happen physically and/or spacially.

nu generalized event abstractor – x1 is a state/process/achievement/activity of <BRIDI>.

Let's see an example:
mi gleki lo nu do dunda lo mlatu ku kei ku
I am happy about (the event of) you donating the cat.

As seen in the definition of gleki, the x2 can be either an event or a state, which means that filling it with "lo nu <BRIDI> kei ku" is appropriate.

Two more examples:
mi tavla do lo nu do ctuca kei ku
I talk to you about (the event of) you teaching.
mi nelci lo nu lo mlatu ku pelxu kei ku
I like (the state of) the cat being yellow

This last example is slightly different, as nu is now being used as a state abstractor. In Lojban, the term "state" generally refers to an event considered as something that is either happening or not happening, with sharp boundaries.

du'u: predication abstractor

The construct du'u...kei treats the bridi in between as a predication.

du'u predication/bridi abstractor – x1 is the predication of <BRIDI>, as expressed in sentence x2.

Let's see an example:

mi djuno lo du'u do pendo mi kei ku
I know (the fact) that you are my friend.

As seen in the definition of djuno, the x2 is a fact, which must be a predication. Notice that "mi djuno lo nu do pendo mi kei ku" would not work, as one can only know facts/predications, not events or states.

One more example:

lo prenu ku ctuca fi lo du'u lo zdani ku pelxu kei ku
The person teaches (the idea) that the house is yellow.

Note that, in principle, "the house being yellow" could be viewed either as a state (lo nu lo zdani ku pelxu kei ku) or as a predication (lo du'u lo zdani ku pelxu kei ku). However, in the context of ctuca, only a predication makes sense, and hence only du'u is appropriate. But there are also situations in which more than one abstractor may be valid in the same sentence – yielding subtle differences in meaning or emphasis.

Finally, note that the sentence above asserts "the person is teaching", but does not assert the nested proposition "the house is yellow". It could be that the house is actually blue, and the person is teaching something untruthful. On the other hand, placing lo nu lo zdani ku pelxu kei ku anywhere within a bridi, without additional context, would generally imply, at least implicitly, that the house is (or was or will be) yellow. (More precisely, it would imply that there exists at least one event of the house being yellow.)

se du'u: indirect quotation

If you look carefully at the definition of du'u, you will notice that, besides the abstract predication itself (x1), it also has a second sumti place for the text of the predication (x2). Hence, "X se du'u do pendo mi kei" means "X is the text corresponding to the predication of you being my friend".

This is often used for indirect quotation. For a concrete example, let's use the word cusku:

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

do cusku lo se du'u do pendo mi kei ku
You say (the text corresponding to the predication) that you are my friend.

As se du'u is recognized as an indirect quotation, imagine quoting the text behind the predication. If it seems confusing, try to substitute "that" to show the indirectness of the quote. Also notice how do cusku lo se du'u do pendo mi kei ku – "You say that you are my friend" is different from "You say 'you are my friend'" (which we are yet to learn how to express in Lojban).

Final example:

mi cusku lo se du'u do dunda lo mlatu ku mi kei ku
I say (the text corresponding to the predication) that you donate the cat to me.

Choosing the appropriate abstractor

When should you use one abstractor instead of the others?

More often than not, the definition of the gismu will include the explicit abstraction of a place. If not, ask yourself the following question: "Do I wish to make the place an event, a state, a predicate, or the text behind the predicate?"


It's now time for you to attempt a few more translations. You will need the following new word:

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

Translate the following sentences from Lojban into English:

Sentence Possible translation
do nupre lo nu tavla mi kei ku You promised that (you) would talk to me.
do cusku lo sedu'u mi nelci lo mlatu ku kei ku You said that I like cats.
mi gleki lo nu lo zdani ku pelxu kei ku I am happy that the house is yellow.
xu do djuno lo du'u lo prenu ku ctuca lo gerku ku kei ku Did you know that people teach dogs?

Now, translate the following sentences from English into Lojban:

Sentence Possible translation
Did you say that the cat is beautiful? xu do cusku lo sedu'u lo mlatu ku melbi kei ku
I am glad that you taught me. mi gleki lo nu do ctuca mi kei ku
What do you know that I did? do djuno lo du'u mi mo kei ku
What did you promise that you would donate to me? do nupre lo nu do dunda ma mi kei ku
[or] do nupre lo nu dunda ma mi kei ku

Final remarks

It may be helpful to memorize "se du'u" as a single construct, which indicates that what follows is an indirect quotation, instead of always mentally decomposing it into se + du'u. Indeed, some people even write "lo sedu'u" instead of "lo se du'u". This is allowed, since "se" and "du'u" are cmavo ("structure words") and in Lojban it is valid to concatenate arbitrary sequences of cmavo together, without spaces, as if they were a single word. That is why "se du'u" is commonly seen as "sedu'u", and "lo nu/du'u/se du'u" is sometimes seen as "lonu/lodu'u/losedu'u". We will learn more about the morphological classes later.


As usual, before proceeding to the next lesson, get some practice with interactive exercises – smash that "Practice" button below!

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
    • Abstractions (su'u...kei, nu...kei and du'u...kei)
      • Mention that it is not always necessary to explicitly mention all places, sometimes they can be inferred from the context
        • Example: "do nupre lo nu do dunda lo mlatu ku kei ku" versus "do nupre lo nu dunda lo mlatu ku kei ku"
      • Emphasize that "nu" may be used for both events and states
  • New exercises
    • Choose "lo nu" vs "lo du'u" vs "lo se du'u" (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)


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)


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