# Lojban Wave Lessons/6

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 Lojban Wave Lessons: Foreword | ← Lesson 5 | Lesson 6 | Lesson 7 →

## Lesson 6: Abstractions

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 can 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. Looking at the definition for happy, which is gleki

gleki = x1 is happy about x2 (event/state)

we can see that the x2 needs to 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 words su'u...kei is a generic convert bridi to selbri function, and works just like loku.

su'u = x1 is an abstraction of {bridi} of type x2
kei = end abstraction

Example:

 melbi su'u dansu keiBeautiful dancing/Beautiful dance
melbi = x1 is beautiful to x2.
dansu = x1 dances to accompaniment/music/rhythm x2.

It's usually hard to find good uses of a bridi as a selbri. However, since su'u BRIDI kei is a selbri, one can convert it to a sumti using lo...ku.

Now we have the equipment to express I am happy that you are my friend. Try it out!

pendo = x1 is a friend of x2

Answer: mi gleki lo su'u do pendo mi kei ku

However, su'ukei does not see much use. People prefer to use the more specific words nukei and du'ukei. They work the same way, but mean something different. nu…kei treats the bridi in between as an event or state, and du'u…kei treats it as an abstract bridi, for expressing things like ideas, thoughts or truths. All these words (except kei) are called abstractors. There are many of them, and only few are used much. su'u…kei is a general abstractor, and will work in all cases.

nu = x1 is an event of (bridi)
du'u = x1 is the predication of (bridi), as expressed in sentence x2

Use nu to say I'm happy about talking to you.

tavla = x1 talks to x2 about subject x3 in language x4.

Answer: mi gleki lo nu tavla do kei ku (notice both the English and the Lojban is vague as to who is doing the talking).

Other important abstractors include: ka...kei (property/aspect abstraction), si'o...kei (concept/idea abstraction), ni...kei (quantity abstraction) among others. The meanings of these is a complicated matter, and will be discussed much later, in lesson twenty-nine. For now, you'll have to do without them.

It is important to notice that some abstractors have several sumti places. As an example, du'u can be mentioned. du'u is defined:

du'u = abstractor. x1 is the predicate/bridi of (bridi) expressed in sentence x2.

The other sumti places besides x1 is rarely used, but lo se du'u (bridi) kei ku is sometimes used as a sumti for indirect quotation: I said that I was given a dog can be written mi cusku lo se du'u mi te dunda lo gerku ku kei ku, if you will pardon the weird example.

cusku = x1 expresses x2 to x3 through medium x4
gerku = x1 is a dog of race x2
 Lojban Wave Lessons: Foreword | ← Lesson 5 | Lesson 6 | Lesson 7 →