The following cmavo is discussed in this section:

Consider the English sentence:

What does it mean? Two possible readings are:

This ambiguity is quite different from the simple tanru ambiguity described in Section 5.2 . We understand that “girls' school” means “a school where girls are the students” , and not “a school where girls are the teachers” or “a school which is a girl” (!). Likewise, we understand that “little girl” means “girl who is small” . This is an ambiguity of grouping. Is “girls' school” to be taken as a unit, with “little” specifying the type of girls' school? Or is “little girl” to be taken as a unit, specifying the type of school? In English speech, different tones of voice, or exaggerated speech rhythm showing the grouping, are used to make the distinction; English writing usually leaves it unrepresented.

Lojban makes no use of tones of voice for any purpose; explicit words are used to do the work. The cmavo bo (which belongs to selma'o BO) may be placed between the two brivla which are most closely associated. Therefore, a Lojban translation of Example 5.17 would be:

Example 5.18 might be translated:

The bo is represented in the literal translation by a bracketed hyphen (not to be confused with the bare hyphen used as a placeholder in other glosses) because in written English a hyphen is sometimes used for the same purpose: “a big dog-catcher” would be quite different from a “big-dog catcher” (presumably someone who catches only big dogs).

Analysis of Example 5.19 and Example 5.20 reveals a tanru nested within a tanru. In Example 5.19 , the main tanru has a seltau of cmalu and a tertau of nixli bo ckule ; the tertau is itself a tanru with nixli as the seltau and ckule as the tertau. In Example 5.20 , on the other hand, the seltau is cmalu bo nixli (itself a tanru), whereas the tertau is ckule . This structure of tanru nested within tanru forms the basis for all the more complex types of selbri that will be explained below.

What about Example 5.21 ? What does it mean?

The rules of Lojban do not leave this sentence ambiguous, as the rules of English do with Example 5.16 . The choice made by the language designers is to say that Example 5.21 means the same as Example 5.20 . This is true no matter what three brivla are used: the leftmost two are always grouped together. This rule is called the “left-grouping rule” . Left-grouping in seemingly ambiguous structures is quite common – though not universal – in other contexts in Lojban.

Another way to express the English meaning of Example 5.19 and Example 5.20 , using parentheses to mark grouping, is:

Because “type-of” is implicit in the Lojban tanru form, it has no Lojban equivalent.

Note: It is perfectly legal, though pointless, to insert bo into a simple tanru:

is a legal Lojban bridi that means exactly the same thing as Example 5.13 , and is ambiguous in exactly the same ways. The cmavo bo serves only to resolve grouping ambiguity: it says nothing about the more basic ambiguity present in all tanru.