Chapter 15. Complex Selbri & Tanru#

Tanru: Metaphorical Combination#

A tanru is formed by placing two or more brivla together as the selbri. The first word (the seltau) modifies the second (the tertau), which carries the primary meaning.

mi sutra bajra I quick-type run → I run quickly / I am a quick runner.

la .djan. barda nanla John big boy → John is a big boy.

le zarci cu melbi zdani The store is a beautiful home-type. → The store is like a beautiful home (in some way).

The relationship between seltau and tertau is always vague — "X-type-of Y" — and the exact meaning depends on context. This is intentional: tanru are a productive, poetic tool, like English compound nouns.

Possible readings of klama jubme (goer table):

• a table that goes (wheeled)
• a table owned by a traveler
• a table for people who travel
• a table associated with going in some way

Lojban does not force a single reading. The speaker chooses a tanru for its evocativeness; the listener infers from context.

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Left-Grouping: The Default Rule#

When three or more brivla appear in a tanru without explicit grouping, left-grouping applies: the leftmost two bind first.

ta cmalu nixli ckule = ta (cmalu nixli) ckule That is a (small-girl)-type school.

The innermost tanru is cmalu nixli (small-girl), which then modifies ckule (school). So this is a school for small girls.

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bo: Right-Grouping#

bo causes the two brivla immediately surrounding it to bind more tightly than their neighbors. This creates right-grouping for those two words:

ta cmalu nixli bo ckule = ta cmalu (nixli ckule) That is a small (girls'-school). → a small school for girls

vs.

ta cmalu bo nixli ckule = ta (cmalu nixli) ckule = left-grouping (same as default here) That is a (small-girl)-type school.

Multiple bo also groups right-to-left:

ta cmalu bo nixli bo ckule = ta cmalu (nixli (... ckule))

The bo binds the last two it appears adjacent to. So A bo B bo C = A (B-bo-C), not (A-bo-B) C.

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ke … ke'e: Explicit Parentheses#

ke opens a grouping bracket and ke'e closes it (elidable at the end of a selbri). Everything inside is treated as a single tanru component:

ta ke melbi cmalu ke'e nixli ckule = ta (melbi cmalu) nixli ckule That is a ((beautiful small) girl)-type school.

ta melbi ke cmalu nixli ke'e ckule = ta melbi (cmalu nixli) ckule That is a beautiful (small-girl)-type school.

ke…ke'e is more readable than bo for complex groupings. It's like mathematical parentheses.

The five distinct groupings of melbi cmalu nixli ckule (beautiful / small / girl / school):

Notes:

• melbi cmalu = "beautifully small" — the first combines with the second
• The bo rule is right-grouping: the rightmost pair groups first
• The final ke'e in the last form is elidable at end of selbri
• English "pretty little girls' school" has only 2 parseable groupings in speech (stress/tone); Lojban has 5 and can distinguish all of them in writing

For comparison, the three-word cmalu nixli ckule already has the CLL "little girls' school" ambiguity:

Adding melbi at the front multiplies the possibilities because melbi can bind with (cmalu), with (cmalu nixli), or can stand alone before the whole rest.

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je: Logical Connection Within Tanru#

When you want a thing to be both X and Y (not "X-type of Y"), use je between the two brivla in the seltau position:

barda je xunre gerku (big and red) type-of dog → a dog that is both big and red

Without je:

barda xunre gerku = (big-type-of-red) dog → a dog whose redness is big (weird!)

The je resolves the independence of two properties:

ta blanu je zdani That is blue and is a house. (separately both, not "a blue-type house")

Other jeks work the same way inside tanru:

le bajra cu jinga ja te jinga The runner is a winner or a loser.

xamgu jo tordu nuntavla (good iff short) speech → speech that is good if and only if it is short

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co: Tanru Inversion#

Normally in a tanru, the last brivla is the head (the tertau). co inverts this: the word after co becomes the modifier, and the word before co becomes the head.

le gerku cu melbi = The dog is beautiful. le gerku cu melbi zdani = The dog is a beautiful-type home. le gerku cu zdani co melbi = The dog is a beautiful-type home. (same meaning, inverted)

More practically, co lets the main predicate come first, with the modifier following:

mi tavla co lojbo I speak in a Lojban-type manner. → I speak Lojbanically.

co has the widest scope of any tanru operator — it spans the whole selbri. Only one co can appear in a selbri at a time.

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je'i, joi and Other Connectives in Selbri#

joi in the seltau position creates a mixed mass tanru — the subject is "an inseparable mix" of two properties:

mi sofybakni joi xirma I am an inseparable-mix of (sofa-cow) and horse. (exotic example)

In practice joi is more commonly used between sumti (see Chapter 8), but it's grammatically valid inside selbri too.

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na'e and to'e in Tanru#

The scalar negation particles na'e and to'e (from Chapter 13) bind directly to a single brivla within a tanru:

mi na'e sutra bajra I (non-fast) run. → I run at a non-normal speed.

mi to'e sutra bajra I slowly run.

le to'e melbi prenu The ugly person.

They do not negate the whole tanru — just the brivla they precede.

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Tense, NA, and negation: where to look#

CLL threads tense, bridi negation, and scalar negation through the selbri in one long narrative. Friendly material splits by topic — use this map when you want “everything that can attach to a selbri”:

na (false) and na'e (non-) are different devices; tenses attach to selbri or bridi in stacks — order can matter. See Chapter 13 for na vs nai vs jo'ai, and Chapter 9 for tense–modal ordering.

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Place Structures of Tanru#

A tanru's place structure is always that of its tertau (the final/main brivla). The seltau's places are irrelevant to the bridi:

mi sutra klama le zarci I quickly go to the store.

Here sutra modifies klama, but the sumti slots are those of klama (x₁=goer, x₂=destination, etc.). The "speed" implied by sutra is inferred, not a numbered slot.

This is why tanru are semantically vague but grammatically clean: only the tertau's place structure is imposed.

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JAI: Converting Tags into Selbri#

jai is a special operator that converts a tense or modal tag into a selbri component, and simultaneously shifts the x₁ place.

Without jai, a modal tag like mu'i (because of / with motive) can only appear as a free prefix before the selbri:

mu'i le nu mi djica cu klama [With motive: my wanting] I go. (mu'i = motivated-by tag)

With jai, the tag becomes part of the selbri, and x₁ of the new selbri is the referent of the tag's value:

le nu mi djica cu jai mu'i klama My wanting is the motive for the going. (x₁ = le nu mi djica, filling the mu'i slot)

The most common use is with fai — the special place created by jai for the original x₁:

le nu mi djica cu jai mu'i klama fai mi My wanting is what motivates the going, which is done by me. (fai mi = the original x₁ "I" is pushed to fai)

jai with FA tags: when combined with a plain FA tag (like tu'a), jai converts the sumti into an appropriate selbri:

le gerku cu jai gau klama = The dog is the agent of going. (jai gau = agentive)

Practical common use — jai gau:

gau (the agent-of BAI cmavo) combined with jai is a clean way to express "causes X to happen":

mi jai gau cadzu le nanmu I cause the man to walk. (literally: I am the gau-agent of the man's walking)

This is more precise than using a causative tanru, because jai gau explicitly invokes the BAI causal role.

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Why ke/ke'e Exists: The Grammar Perspective#

You already know that ke…ke'e creates parenthetical grouping in tanru. But why is this a dedicated cmavo pair, rather than just how juxtaposition works?

The formal grammar defines tanru as a sequence of selbri components with left-grouping as the default. This means the grammar can't interpret "extra" juxtaposition as "tighter binding" without ambiguity. There is no way for the parser to know, from word order alone, that three brivla A B C should group as A (B C) rather than (A B) C.

bo resolves this for a pair — it marks the two words around it as a tightly-bound unit. But bo can only group two things at a time, and nesting bo bo bo… quickly becomes unreadable.

ke solves the general case: it acts as an opening parenthesis in the grammar, and ke'e is the explicit closing parenthesis. This gives the parser a clear left-bracket at an arbitrary point in the tanru sequence:

le melbi ke cmalu nixli ke'e ckule
       [        opens here        ]
= melbi [(cmalu nixli)] ckule

The grammar rule is: after seeing ke, the parser begins collecting a sub-selbri until it sees ke'e (or until the selbri ends, at which point an elided ke'e is assumed).

ke'e is almost always elidable at the end of the tanru, because the end of the selbri naturally closes it — but it is required when the grouping ends mid-tanru and another component follows. Compare:

le melbi ke cmalu nixli ke'e ckule — ke'e required (more components follow) le ckule ke cmalu nixli — ke'e elidable (tanru ends here)

The same ke/ke'e pair also works with connectives — connecting whole phrases inside a tanru bracket:

le ke cmalu ja barda ke'e nixli The (small or large) girl (ja = or, connecting the two modifiers as a unit)

Without ke, the ja would only connect the two words on either side of it. With ke, it spans the whole grouped phrase.

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me: Turning Sumti into Selbri#

Any sumti can be converted into a selbri using me:

le gerku cu me la fido. The dog is Fido-type. = The dog is like Fido / is Fido.

me creates a selbri meaning "is [the thing described by sumti]". It's used to:

• Make a sumti into a type: mi me la .lojban. = I am a Lojban-type person
• Borrowed or long names: le zgike cu me la'o gy. Beethoven gy. = the music is Beethoven-type (style associated with that name)

Close the me phrase with me'u (elidable at end of selbri):

le me la .alis. me'u cu melbi The Alice-type thing is beautiful.

me is particularly useful with cmavo that normally aren't selbri:

le se cusku be mi cu me zo blanu What I said was the-word-"blanu"-type. = I said the word "blanu".

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Other Kinds of Simple Selbri#

Besides brivla and tanru, several constructions yield a selbri:

Number words as selbri:

mi ci — I am three / I am the third le ci prenu — the three people (ci quantifies prenu)

Numbers and other PA cmavo can serve as predicates of quantity or ordinal:

le vo prenu cu xabju ti — The four people live here.

moi (ordinal) and other MOI cmavo:

mi pamoi — I am first. do remoi — You are second.

le nanmu pu klama le cimoi dinju The man went to the third building. (cimoi = ci + moi, third; not romoi, which would be ro + moi)

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Tanru Taxonomy: Patterns of Meaning#

Tanru meaning is deliberately vague — the exact relationship between seltau and tertau is left for context to determine. But in practice, tanru tend to fall into recognizable patterns. Knowing these patterns helps you both interpret and construct tanru naturally.

Asymmetrical Tanru#

In asymmetrical tanru, word order matters: clock pendulum is the type of pendulum used in clocks, while pendulum clock is the type of clock that uses a pendulum. Most tanru are asymmetrical.

Seltau = object of the tertau's action

The seltau names what the tertau-action is applied to or directed at:

Seltau = element type, tertau = the set

The seltau describes what the members of the tertau group are:

Seltau = whole object, tertau = a part of it

The seltau names the whole; the tertau is a component or detail of that whole:

Seltau = purpose or goal

The seltau describes what the tertau is for or aimed at:

Seltau = material

The seltau names the substance the tertau is made of:

Seltau = resemblance

The tertau resembles the seltau in some relevant way:

Seltau = location or time context

The seltau specifies where or when the tertau's referent belongs:

Symmetrical Tanru#

In symmetrical tanru, order does not significantly affect meaning — either word could come first. These often correspond to logical conjunction with je.

Things that are correctly described by both components

These are tanru where the referent genuinely fits both the seltau and the tertau. They could be rephrased with je (and):

Note that remna nakni means essentially the same as nakni remna — both describe something that is both human and male. This symmetry distinguishes these from cases where order matters.

Using These Patterns#

When you form a tanru, you are picking the pattern implicitly. When someone hears your tanru, they use pragmatics — the surrounding context — to decide which pattern fits best. This is by design: Lojban tanru are deliberately ambiguous. If you need precision, either:

1. Explain in context — let the surrounding bridi make the meaning clear
2. Convert to lujvo — a compound word with a fixed, agreed meaning
3. Use explicit connectives — je for "both", non-logical connectives for mixtures, etc.

The tanru system lets you coin new combinations freely. The cost is vagueness; the benefit is expressiveness and flexibility.

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Summary#

Tense / negation map: na vs na'e/to'e vs tense cmavo — see Tense, NA, and negation: where to look above.

Rules:

• Default tanru is left-grouping: A B C = (A B) C
• bo = right-group its two neighbors: A B bo C = A (B C)
• ke…ke'e = explicit grammar brackets; ke'e required when grouping ends mid-tanru
• je = both properties hold independently (not "A-type-of B")
• co = wide-scope inversion, one per selbri
• jai = tag-to-selbri conversion; the tag's value becomes x₁
• Tanru inherits tertau's place structure
• me = sumti → selbri (the sumti becomes a type)

Tanru taxonomy (patterns of meaning):

• Tanru meaning is deliberately vague; context determines the relationship
• Asymmetrical tanru: order matters; common patterns include seltau as object of action, material, location, purpose, resemblance, etc.
• Symmetrical tanru: order doesn’t affect core meaning; often equivalent to je (logical AND): remna nakni = human male = remna je nakni
• If precision is needed: explain in context, convert to lujvo, or use explicit connectives