immediately vs straight off

immediately and straight off both are adverbs.

Word	Noun	Adjective	Verb	Adverb
immediately	No	No	No	Yes
straight off	No	No	No	Yes

As adverbs, immediately and straight off are synonyms defined as:

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

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

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