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Bridi and jufra

Bridi is the most central unit of Lojban utterances. The concept is very close to what we call a proposition in English. A bridi is a claim that some objects stand in a relation to each other, or that an object has some property. This stands in contrast to jufra, which are merely sentences, which can be bridi or anything else being said. The difference between a bridi and a jufra is that a jufra does not necessarily state anything, while a bridi does. Thus, a bridi might be true or false, while not all jufra can be said to be such.

To have some examples (in English, to begin with), "Mozart was the greatest musician of all time" is a bridi, because it makes a claim with a truth value, and it involves an object, Mozart, and a property, being the greatest musician of all time. On the contrary, "Ow! My toe!" is not a bridi, since it does not involve a relation, and thus does not state anything. Both, though, are jufra.

Try to identify the bridi among these English jufra:

  1. I hate it when you do that.
  2. Woah, that looks delicious!
  3. Geez, not again.
  4. No, I own three cars
  5. Nineteen minutes past eight.
  6. This Saturday, yes.

Answers: 1, 2 and 4 are bridi. The rest contain no relation or claim of a property.

Put in Lojban terms, a bridi consists of one selbri, and one or more sumti. The selbri is the relation or claim about the object, and the sumti are the objects which are in a relation. Note that object is not a perfect translation of sumti, since sumti can refer to not just physical objects, but also purely abstract things like "the idea of warfare". A better translation would be something like "subject, direct or indirect object" for sumti, and main verb for selbri, though, as we will see, this is not optimal either.

We can now write the first important lesson down: bridi = selbri + one or more sumti.

Identify the sumti and selbri equivalents in these English jufra:

  1. I will pick up my daughters with my car.
    • Answer: selbri: pick up (with) — sumti: I, my daughters, my car
  2. He bought 5 new shirts from Mark for just two hundred euro!
    • Answer: selbri: bought (from) (for) — sumti: He, 5 new shirts, Mark and two hundred euros
  3. So far, the EPA has done nothing about the amount of sulphur dioxide.
    • Answer: selbri: has done (about) — sumti: The EPA, nothing and the amount of sulphur dioxide

Constructing simple bridi

Now let's try making some Lojban bridi. For this we will need some words to act as selbri:

dunda x1 gives x2 to x3 (without payment).

pelxu x1 is yellow.

zdani x1 is a home of x2.

Notice that these words meaning "give", "yellow" and "home" would be considered a verb, an adjective and a noun in English. In Lojban, there are no such categories and no such distinction. dunda can be translated as "gives" (verb), "is a giver" (noun), "is giving" (adjective) as well as to an adverb form. They all act as selbri, and are used in the same way.

We will also need a few words to act as sumti:

mi "I" or "we" – the one or those who are speaking.

ti "this" – some thing(s) or event(s) near the speaker(s), possibly pointed to by them.

do "you" – the one or those who are being spoken to.

ta "that" – some thing(s) or event(s) near the listener(s), possibly pointed to by them.

See the strange translations of the selbri above – especially the x1, x2 and x3? Those are called sumti places. They are places where sumti can go to fill a bridi. Filling a sumti in a place states that the sumti fits in that place. The second place of dunda, for example, x2, is the thing being given. The third is the object which receives the thing. Notice also that the translation of dunda has the word "to" in it. This is because, while this word is needed in English to signify the receiver, the receiver is in the third sumti place of dunda. So when you fill the third sumti place of dunda, the sumti you fill in is always the receiver, and you don't need an equivalent to the word "to"!

To say a bridi, you simply say the first sumti (x1), then the selbri, then any other sumti (x2, x3 and so on).

Usual bridi: (x1 sumti) (selbri) (x2 sumti) (x3 sumti) (x4 sumti) (x5 sumti) (and so on)

So, how would you say the following sentences in Lojban?

Sentence Possible translation
This is a home of me. ti zdani mi
You give this to me. do dunda ti mi

Now, how would you translate the following sentences into English?

Sentence Possible translation
ti pelxu This is yellow.
ta zdani do That is a home of you / That is your house.
mi dunda ti do I give this to you.

Quite easy once you get the hang of it, right?


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
    • Start with brief note about sounds, and point to some resource (cancelled; moved to course description)
    • Basic concepts: jufra/bridi/selbri/sumti
      • Definitions
        • Explain "mi" and "do"
        • Explain "ti" and "ta"
      • Examples in English
      • Examples in Lojban
      • Syntax tree
        • selbri as root and sumti as children
        • edges labeled "x1", "x2", ...
  • New exercises
    • Given an English sentence, choose "bridi and jufra" or "only jufra" (OK)
    • Given a Lojban sentence, choose "bridi and jufra" or "only bridi" (OK)
    • Given a bridi, identify its selbri (OK)
    • Given a bridi, tell its place structure (OK)
      • Example: "Select the x2", "Select the listener"
      • This can also be used for sentences that are not automatically generated, and this is very useful for vocabulary lessons
    • Translations from English to Lojban (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


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


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