The following cmavo is discussed in this section:

The normal Lojban sentence is just a bridi, parallel to the normal English sentence which has a subject and a predicate:

In Chinese, the normal sentence form is different: a topic is stated, and a comment about it is made. (Japanese also has the concept of a topic, but indicates it by attaching a suffix; other languages also distinguish topics in various ways.) The topic says what the sentence is about:

The colon in the first two versions of Example 19.3 separate the topic ( “this news”) from the comment ( “I know already”).

Lojban uses the cmavo zo'u (of selma'o ZOhU) to separate topic (a sumti) from comment (a bridi):

Example 19.4 is the literal Lojban translation of Example 19.3. Of course, the topic-comment structure can be changed to a straightforward bridi structure:

Example 19.5 means the same as Example 19.4 , and it is simpler. However, often the position of the topic in the place structure of the selbri within the comment is vague:

Is the fish eating or being eaten? The sentence doesn't say. The Chinese equivalent of Example 19.6 is:

which is vague in exactly the same way.

Grammatically, it is possible to have more than one sumti before zo'u. This is not normally useful in topic-comment sentences, but is necessary in the other use of zo'u : to separate a quantifying section from a bridi containing quantified variables. This usage belongs to a discussion of quantifier logic in Lojban (see Section 16.2), but an example would be:

The string of sumti before zo'u (called the “prenex” : see Section 16.2) may contain both a topic and bound variables:

To specify a topic which affects more than one sentence, wrap the sentences in tu'e … tu'u brackets and place the topic and the zo'u directly in front. This is the exception to the rule that a topic attaches directly to a sentence:

Note: In Lojban, you do not “want money” ; you “want to have money” or something of the sort, as the x₂ place of djica demands an event. As a result, the straightforward rendering of Example 19.9 without a topic is not:

where ri means loi jdini and is interpreted as “the mere existence of money” , but rather:

namely, the possession of money. But topic-comment sentences like Example 19.10 are inherently vague, and this difference between ponse (which expects a physical object in x₂) and djica is ignored. See Example 19.45 for another topic/comment sentence.

The subject of an English sentence is often the topic as well, but in Lojban the sumti in the x₁ place is not necessarily the topic, especially if it is the normal (unconverted) x₁ for the selbri. Thus Lojban sentences don't necessarily have a “subject” in the English sense.