A comma should be used to separate two or more co-ordinate adjectives that describe the same noun. Or to put it more simply, if you’re using two similar words to describe a thing, person, place, animal or idea you should use a comma to separate them. She worked in a happy, relaxed office.

Coordinate adjectives are words that apply to and describe some attribute of the same noun or subject. To do this effectively, however, the author must separate them by a comma—otherwise the reader may confuse the adjectives as a singular modifier and not a coordinate pair.

Coordinate adjectives are adjectives that appear in sequence to modify the same noun. She bought the bright, shiny Volvo because it suited her tastes.

You should use a comma between two adjectives when they are coordinate adjectives. Coordinate adjectives are two or more adjectives that describe the same noun equally. With coordinate adjectives you can put “and” between them and the meaning is the same. Similarly, you can swap their order.

Common Subordinators

Subordinators in English grammar are words including the function word that that introduce dependent or subordinate clauses including noun clauses, adjective clauses, and adverb clauses. The term noun clause marker is also used for subordinating conjunctions that introduce noun clauses.

A clause is a group of words that contains a verb (and usually other components too). A clause may form part of a sentence or it may be a complete sentence in itself. For example: He was eating a bacon sandwich.