A modifier describes another word or word group. Words, phrases
(groups of words without a subject or predicate, usually
introduced by a preposition or conjunction), and clauses (groups
of words with a subject and verb within a compound or complex
sentence) may all be modifiers. An adjective modifies a noun or
a pronoun. An adverb modifies a verb, an adjective, another
adverb, or a clause. Clauses or phrases may serve as adjectives
or adverbs.