lat vs latissimus dorsi

lat and latissimus dorsi both are nouns.

Word	Noun	Adjective	Verb	Adverb
lat	Yes	No	No	No
latissimus dorsi	Yes	No	No	No

As nouns, lat and latissimus dorsi are synonyms defined as:

lat and latissimus dorsi: a broad flat muscle on either side of the back

lat (noun)	latissimus dorsi (noun)
a broad flat muscle on either side of the back	a broad flat muscle on either side of the back