narrow vs pin down

narrow is a noun but pin down is not a noun.

Word	Noun	Adjective	Verb	Adverb
narrow	Yes	Yes	Yes	No
pin down	No	No	Yes	No

As verbs, narrow and pin down are synonyms defined as:

Other synonyms of narrow include nail down, narrow down, peg down, specify.

narrow (noun)	pin down (noun)
a narrow strait connecting two bodies of water

narrow (adjective)	pin down (adjective)
not wide
very limited in degree
lacking tolerance or flexibility or breadth of view
characterized by painstaking care and detailed examination
limited in extent or scope

narrow (verb)	pin down (verb)
make or become more narrow or restricted	define clearly
become tight or as if tight	attach with or as if with a pin
become more focused on an area of activity or field of study	place in a confining or embarrassing position
define clearly