Noun modifiers are words or phrases that provide additional information about a noun, helping to describe, specify, or quantify it. We sometimes have two nouns together to demonstrate that one thing is a part of something else. In the following examples, the first noun is called a noun modifier.
Noun modifiers can be used to show what something is made of.
Noun modifiers can be used to demonstrate a measurement.
Noun modifiers can be used with nouns ending in –er.