purpose vs decide

purpose is a noun but decide is not a noun.

Word	Noun	Adjective	Verb	Adverb
purpose	Yes	No	Yes	No
decide	No	No	Yes	No

As verbs, decide is a hypernym of purpose; that is, decide is a word with a broader meaning than purpose:

Other hypernyms of purpose include determine, make up one's mind.

purpose (noun)	decide (noun)
what something is used for
the quality of being determined to do or achieve something; firmness of purpose
an anticipated outcome that is intended or that guides your planned actions

purpose (verb)	decide (verb)
reach a decision	reach, make, or come to a decision about something
propose or intend	bring to an end; settle conclusively
	cause to decide
	influence or determine