## 5.8. Inversion of tanru: co

The following cmavo is discussed in this section:

 co CO tanru inversion marker

The standard order of Lojban tanru, whereby the modifier precedes what it modifies, is very natural to English-speakers: we talk of blue houses, not of houses blue. In other languages, however, such matters are differently arranged, and Lojban supports this reverse order (tertau before seltau) by inserting the particle co. Example 5.76 and Example 5.77 mean exactly the same thing:

Example 5.76.

 ta blanu zdani That is-a-blue type-of-house.
 That is a blue house.

Example 5.77.

 ta zdani co blanu That is-a-house of-type blue.
 That is a blue house.

This change is called tanru inversion. In tanru inversion, the element before co (zdani in Example 5.77) is the tertau, and the element following co (blanu) in Example 5.77) is the seltau.

The meaning, and more specifically, the place structure, of a tanru is not affected by inversion: the place structure of zdani co blanu is still that of zdani. However, the existence of inversion in a selbri has a very special effect on any sumti which follow that selbri. Instead of being interpreted as filling places of the selbri, they actually fill the places (starting with x2) of the seltau. In Section 5.7, we saw how to fill interior places with bebeibe'o, and in fact Example 5.78 and Example 5.79 have the same meaning:

Example 5.78.

 mi klama be le zarci bei le zdani be'o troci I am-a-(goer to the market from the house ) type-of-trier.
 I try to go to the market from the house.

Example 5.79.

 mi troci co klama le zarci le zdani I am-a-trier of-type (goer to-the market from-the house).
 I try to go to the market from the house.

Example 5.79 is a less deeply nested construction, requiring fewer cmavo. As a result it is probably easier to understand.

Note that in Lojban trying to go is expressed using troci as the tertau. The reason is that trying to go is a going type of trying, not a trying type of going. The trying is more fundamental than the going – if the trying fails, we may not have a going at all.

Any sumti which precede a selbri with an inverted tanru fill the places of the selbri (i.e., the places of the tertau) in the ordinary way. In Example 5.79, mi fills the x1 place of troci co klama, which is the x1 place of troci. The other places of the selbri remain unfilled. The trailing sumti le zarci and le zdani do not occupy selbri places, despite appearances.

As a result, the regular mechanisms (involving selma'o VOhA and GOhI, explained in Chapter 7) for referring to individual sumti of a bridi cannot refer to any of the trailing places of Example 5.79, because they are not really sumti of the bridi at all.

When inverting a more complex tanru, it is possible to invert it only at the most general modifier-modified pair. The only possible inversion of Example 5.19, for instance, is:

Example 5.80.

 ta nixli [bo] ckule co cmalu That (is-a-girl type-of school) of-type little.
 That's a girls' school which is small.

Note that the bo of Example 5.19 is optional in Example 5.80, because co groups more loosely than any other cmavo used in tanru, including none at all. Not even keke'e parentheses can encompass a co:

Example 5.81.

 ta cmalu ke nixli ckule [ke'e] co melbi That is-a-(little type-of ( girl type-of school )) of-type pretty.
 That's a small school for girls which is beautiful.

In Example 5.81, the ke'e is automatically inserted before the co rather than at its usual place at the end of the selbri. As a result, there is a simple and mechanical rule for removing co from any selbri: change A co B to ke B ke'e A. (At the same time, any sumti following the selbri must be transformed into bebeibe'o form and attached following B.) Therefore,

Example 5.82.

 ckule co melbi nixli school of-type pretty girl
 school for beautiful girls

means the same as:

Example 5.83.

 ke melbi nixli ke'e ckule ( pretty girl ) school

Multiple co cmavo can appear within a selbri, indicating multiple inversions: a right-grouping rule is employed, as for bo. The above rule can be applied to interpret such selbri, but all co cmavo must be removed simultaneously:

Example 5.84.

 ckule co nixli co cmalu school of-type (girl of-type little)

becomes formally

Example 5.85.

 ke ke cmalu ke'e nixli ke'e ckule ( ( little ) girl ) school

which by the left-grouping rule is simply

Example 5.86.

 cmalu nixli ckule little girl school
 school for little girls

As stated above, the selbri places, other than the first, of

Example 5.87.

 mi klama co sutra I am-a-goer of-type quick
 I go quickly

cannot be filled by placing sumti after the selbri, because any sumti in that position fill the places of sutra, the seltau. However, the tertau places (which means in effect the selbri places) can be filled with be:

Example 5.88.

 mi klama be le zarci be'o co sutra I am-a-goer ( to-the store ) of-type quick.
 I go to the store quickly.