Who and whom both introduce a dependent clause and refer to an antecendent noun. Who in its different forms refers to persons. Which refers to things or animals. That refers to a person, place or thing. Adjectives Adjectives are words that modify nouns and pronouns.
Adjectives describe or limit the meaning of the words they modify.
Adjectives are best used to express concepts that nouns alone cannot convey. Descriptive adjectives describe the noun they modify. These are adjectives like large, small, happy, sad, clean, exhausted, etc. Limiting adjectives limit the meaning of the words they modify. An adverb modifies a verb, an adjective or an adverb.