Adjective forms refer to the different variations of adjectives that describe qualities or characteristics of nouns. The main forms include positive, comparative, and superlative. The positive form describes a quality (e.g., tall), the comparative form compares two nouns (e.g., taller), and the superlative form indicates the highest degree among three or more nouns (e.g., tallest). In English, many one-syllable adjectives form their comparative and superlative by adding "-er" and "-est" respectively. For adjectives with two or more syllables, the words "more" and "most" are often used instead (e.g., beautiful, more beautiful, most beautiful). Understanding these forms helps in making clear comparisons.