In English, every verb is tagged for the grammatical category called tense: past, present, or future. The sentence
17.1) John went to the storenecessarily happens at some time in the past, whereas
17.2) John is going to the storeis necessarily happening right now.
The Lojban sentence
17.3) la djan. [cu] klama le zarci John goes/went/will-go to-the storeserves as a translation of either Example 17.1 or Example 17.2, and of many other possible English sentences as well. It is not marked for tense, and can refer to an event in the past, the present or the future. This rule does not mean that Lojban has no way of representing the time of an event. A close translation of Example 17.1 would be:
17.4) la djan. pu klama le zarci John [past] goes to-the storewhere the tag “pu” forces the sentence to refer to a time in the past. Similarly,
17.5) la djan. ca klama le zarci John [present] goes to-the storenecessarily refers to the present, because of the tag “ca”. Tags used in this way always appear at the very beginning of the selbri, just after the “cu”, and they may make a “cu” unnecessary, since tags cannot be absorbed into tanru. Such tags serve as an equivalent to English tenses and adverbs. In Lojban, tense information is completely optional. If unspecified, the appropriate tense is picked up from context.
Lojban also extends the notion of “tense” to refer not only to time but to space. The following example uses the tag “vu” to specify that the event it describes happens far away from the speaker:
17.6) do vu vecnu zo'e You yonder sell something-unspecified.
In addition, tense tags (either for time or space) can be prefixed to the selbri of a description, producing a tensed sumti:
17.7) le pu bajra [ku] cu tavla The earlier/former/past runner talked/talks.(Since Lojban tense is optional, we don’t know when he or she talks.)
Tensed sumti with space tags correspond roughly to the English use of “this” or “that” as adjectives, as in the following example, which uses the tag “vi” meaning “nearby”:
17.8) le vi bajra [ku] cu tavla The nearby runner talks. This runner talks.Do not confuse the use of “vi” in Example 17.8 with the cmavo “ti”, which also means “this”, but in the sense of “this thing”.
Furthermore, a tense tag can appear both on the selbri and within a description, as in the following example (where “ba” is the tag for future time):
17.9) le vi tavla [ku] cu ba klama The here talker [future] goes. The talker who is here will go. This talker will go.