Classifiers are often nouns. Look above; we have police, Christmas, and wax—all nouns.
But paired with another noun—police car, Christmas tree, wax dummy—they change their function slightly and serve to classify the main noun.
(That said, classifiers can also be adjectives: polar bear, dental appointment, lunar calendar.)
Note: A classifier comes after any pointer or quantifier.
(For more on classifiers, see the lesson on adjective groups).
