left hander vs lefty

left hander and lefty both are nouns.

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

As nouns, left hander and lefty are synonyms defined as:

left hander and lefty: a baseball pitcher who throws the ball with the left hand

Other synonyms of left hander include left-handed pitcher, left-hander, lefthander, southpaw.

left hander (noun)	lefty (noun)
a baseball pitcher who throws the ball with the left hand	a person who uses the left hand with greater skill than the right
	a baseball pitcher who throws the ball with the left hand