denim
Refers to the fabric itself, not necessarily a garment.
このジャケットはデニムでできている。
This jacket is made of denim.
He was wearing a denim jacket.
Commonly used to mean denim jeans or denim clothing in general.
今日はデニムを履いてきた。
I wore jeans today.
I paired denim pants with a white shirt.
Even in summer, she often wears denim.