breeches vs knee breeches

breeches and knee breeches both are nouns.

Word	Noun	Adjective	Verb	Adverb
breeches	Yes	No	No	No
knee breeches	Yes	No	No	No

As nouns, breeches and knee breeches are synonyms defined as:

breeches and knee breeches: (used in the plural) trousers ending above the knee

Other synonyms of breeches include knee pants, knickerbockers, knickers.

breeches (noun)	knee breeches (noun)
(used in the plural) trousers ending above the knee	(used in the plural) trousers ending above the knee