modifier

US /ˈmɑː.də.faɪ.ɚ/
UK /ˈmɑː.də.faɪ.ɚ/
1.

bổ nghĩa

a word or phrase that is used with another word or phrase to limit or add to its meaning:

:
In "safety barrier" the noun "safety" is being used as a modifier.