immediately vs instantly

immediately and instantly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
immediately	No	No	No	Yes
instantly	No	No	No	Yes

As adverbs, immediately and instantly are synonyms defined as:

immediately and instantly: without delay or hesitation; with no time intervening

Other synonyms of immediately include at once, directly, forthwith, like a shot, now, right away, straight off, straightaway.

immediately (adverb)	instantly (adverb)
without delay or hesitation; with no time intervening	without delay or hesitation; with no time intervening
near or close by	without any delay
bearing an immediate relation