nail down vs concretize

nail down and concretize both are verbs.

Word	Noun	Adjective	Verb	Adverb
nail down	No	No	Yes	No
concretize	No	No	Yes	No

As verbs, concretize is a hyponym of nail down; that is, concretize is a word with a more specific, narrower meaning than nail down:

nail down (verb)	concretize (verb)
make final; put the last touches on; put into final form	become specific
define clearly	make something concrete
succeed in obtaining a position