first base vs initiative

first base and initiative both are nouns.

Word	Noun	Adjective	Verb	Adverb
first base	Yes	No	No	No
initiative	Yes	Yes	No	No

As nouns, initiative is a hypernym of first base; that is, initiative is a word with a broader meaning than first base:

Other hypernyms of first base include first step, opening, opening move.

first base (noun)	initiative (noun)
the initial stage in accomplishing something	the first of a series of actions
the fielding position of the player on a baseball team who is stationed at first of the bases in the infield (counting counterclockwise from home plate)	readiness to embark on bold new ventures
the base that must be touched first by a base runner in baseball

first base (adjective)	initiative (adjective)
	serving to set in motion