Noun as Adjective
As you know, a noun is a person, place or thing, and an adjective is a word that describes a noun:
adjective
noun
clever
teacher
small
office
black
horse
Sometimes we use a noun to describe another noun. In that case, the first noun "acts as" an adjective.
noun
as
adjective
noun
history
teacher
ticket
office
race
horse
The "noun as