Instant
Part of speech: noun
Definition: A very short period of time; a moment. A single, usually precise, point in time. An instant beverage or food, especially instant coffee. The current month (abbreviated as: inst.)
Part of speech: adverb
Definition: At once; immediately.
Part of speech: adjective
Definition: Impending; imminent. Urgent; pressing; acute. Occurring immediately; immediate; present. Lasting for a short moment; momentary; short-lived. Very quickly and easily prepared (food or drink), for example instant coffee. Of the current month (abbreviation inst.)
Example sentence: They give birth astride of a grave, the light gleams an instant, then it's night once more.
Instantaneous
Part of speech: adjective
Definition: Occurring, arising, or functioning without any delay; happening within an imperceptibly brief period of time.