A language can only be considered to have a future tense as a grammatical category if its use is required for future events, or it has an optional form that can only be used to mark future events. It can be expressed morphologically (verbal inflection) or periphrastically (using an auxiliary).

Types:

NoFut: The language has no future tense in the grammatical sense. (Future time is not expressed through a grammatically distinct form.)

FutOblInfl: Grammatical expression of future time is required, and it is expressed through verbal inflection (a modified or affixed form of the verb).

FutOptInfl: Grammatical expression of future time is optional; when used, it is expressed through verbal inflection (a modified or affixed form of the verb).

FutOblPfr: Grammatical expression of future time is required, and it is expressed through the use of an auxiliary verb in addition to some form of the main verb, usually nonfinite.[1]

FutOptPfr: Grammatical expression of future time is optional; when used, it is expressed through the use of an auxiliary verb in addition to some form of the main verb, usually nonfinite.[2]

When a language displays more than one type with equal frequency, two values can be listed. If one type is structurally dominant, a slash (/) can separate the two values, with the dominant value appearing first; if neither is dominant, the two are listed with an ampersand (&) separating the two.

[1] The type of nonfinite (uninflected verbal base, infinitive, other nonfinite derived from a verb) should be detailed in the commentary.

[2] The type of nonfinite (uninflected verbal base, infinitive, other nonfinite derived from a verb) should be detailed in the commentary.