left hander vs pitcher

left hander and pitcher both are nouns.

Word	Noun	Adjective	Verb	Adverb
left hander	Yes	No	No	No
pitcher	Yes	No	No	No

As nouns, pitcher is a hypernym of left hander; that is, pitcher is a word with a broader meaning than left hander:

Other hypernyms of left hander include hurler, twirler.

left hander (noun)	pitcher (noun)
a baseball pitcher who throws the ball with the left hand	the position on a baseball team of the player who throws the ball for a batter to try to hit
	an open vessel with a handle and a spout for pouring
	(baseball) the person who does the pitching
	(botany) a leaf that is modified in such a way as to resemble a pitcher or ewer
	the quantity contained in a pitcher