lefty vs lefthander

lefty and lefthander both are nouns.

Word	Noun	Adjective	Verb	Adverb
lefty	Yes	No	No	No
lefthander	Yes	No	No	No

As nouns, lefty and lefthander are synonyms defined as:

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

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

lefty (noun)	lefthander (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