The Distant Future Tense
Also known as: the periphrastic future, anadyatana ("not of today"), luṭ
The distant future tense is used to talk about things that will happen in the distant future. It's easy to learn and easy to use:
यदि पृच्छति तदा गन्तास्मि
yadi pṛcchati tadā gantāsmi
If he asks, then I will go.
यदि पृच्छति तदा गन्ता
yadi pṛcchati tadā gantā
If he asks, then he will go.
The ordinary future tense describes actions that will happen soon and that depend on present circumstances. The distant future tense, meanwhile, describes a remote action that is somehow removed from the present time. It describes things that will not happen for a considerable amount of time, and it is more certain than the ordinary future tense.
Now, let's study the formation of the distant future tense.
The examples above might have reminded you of the -tṛ noun gantṛ. Indeed, that's where the distant future tense comes from: it's a combination of a -tṛ noun and the verb as. Even though this tense is based on a noun, you should consider it to be a real verb form.
In the first and second person, we use the case 1 singular of the masculine -tṛ noun. This inflected noun is followed by as, which is inflected to show the number and person of the verb. The third person, however, is different. Instead of using as, we use the case 1 endings for the -tṛ noun, with no extra verb. As you can imagine, this can create some ambiguity:
He is a killer.
He will kill.
You'll have to rely on context to understand whether the word is a noun or a verb.