tweed vs pair of trousers

tweed and pair of trousers both are nouns.

Word	Noun	Adjective	Verb	Adverb
tweed	Yes	No	No	No
pair of trousers	Yes	No	No	No

As nouns, pair of trousers is a hypernym of tweed; that is, pair of trousers is a word with a broader meaning than tweed:

tweed: (usually in the plural) trousers made of flannel or gabardine or tweed or white cloth
pair of trousers: (usually in the plural) a garment extending from the waist to the knee or ankle, covering each leg separately

Other hypernyms of tweed include pant, trousers.

tweed (noun)	pair of trousers (noun)
thick woolen fabric used for clothing; originated in Scotland	(usually in the plural) a garment extending from the waist to the knee or ankle, covering each leg separately
(usually in the plural) trousers made of flannel or gabardine or tweed or white cloth