purchase vs pick out

purchase is a noun but pick out is not a noun.

Word	Noun	Adjective	Verb	Adverb
purchase	Yes	No	Yes	No
pick out	No	No	Yes	No

purchase (noun)	pick out (noun)
the acquisition of something for payment
the mechanical advantage gained by being in a position to use a lever
a means of exerting influence or gaining advantage
something acquired by purchase

purchase (verb)	pick out (verb)
obtain by purchase; acquire by means of a financial transaction	pick out, select, or choose from a number of alternatives
	detect with the senses