lefty vs left hander

lefty and left hander both are nouns.

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

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

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

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

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