Things I could not discriminate until it was too late, part 1

Linguistics Terms 2

Tense, aspect, and mood

Time is a universal, non-linguistic concept with these divisions: past, present, and future; by tense we understand the correspondence between the form of the verb and our concept of time.

Aspect concerns the manner in which the verbal action is experienced...

...while mood relates the verbal action to such conditions as certainty, obligation, necessity, possibility.

A Concise Grammar of Contemporary English
Randolph Quirk and Sidney Greenbaum