chinos vs pair of trousers

chinos and pair of trousers both are nouns.

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

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

chinos: (plural) trousers made with chino 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 chinos include pant, trousers.

chinos (noun)	pair of trousers (noun)
(plural) trousers made with chino cloth	(usually in the plural) a garment extending from the waist to the knee or ankle, covering each leg separately