second thought vs reconsideration

second thought and reconsideration both are nouns.

Word	Noun	Adjective	Verb	Adverb
second thought	Yes	No	No	No
reconsideration	Yes	No	No	No

As nouns, second thought and reconsideration are synonyms defined as:

second thought and reconsideration: thinking again about a choice previously made

Other synonyms of second thought include afterthought, rethink.

second thought (noun)	reconsideration (noun)
thinking again about a choice previously made	thinking again about a choice previously made
	a consideration of a topic (as in a meeting) with a view to changing an earlier decision