An adjective is a word that modifies a noun or pronoun by describing, identifying, or quantifying words. There are two main kinds of adjectives: physical appearance adjectives and attitude adjectives. Physical appearance adjectives describe attributes like fat, tall, or short, which can influence personality development as people form initial opinions based on physical traits. Attitude adjectives convey dispositions and tendencies to respond positively or negatively to things, with examples being intelligent or ungrateful.