Adjectives

Adjectives of one syllable add -er and -est to their comparative and superlative forms. Adjectives ending with e just add -r and -st. Some adjectives double the final consonant.

PositiveComparativeSuperlative
old older/elder oldest/eldest
nice nicer nicest
big bigger biggest
late later latest/last

Some adjectives of two syllables add -er and -est to their comparative and superlative forms, respectively. Some other adjectives of two syllables use more or less in forming the comparative degree and most or least in forming the superlative degree.

PositiveComparativeSuperlative
narrow narrower narrowest
happy happier happiest
useful more useful most useful
boring more boring most boring

Adjectives of three or more syllables always add more or less and most or least before them to form comparative and superlative degrees.

PositiveComparativeSuperlative
beautiful more beautiful most beautiful
dangerous more dangerous most dangerous
exciting more exciting most exciting

There are a few adjectives which have irregular forms of comparative and superlative degrees. These you will have to learn by heart.

PositiveComparativeSuperlative
good/well better best
bad worse worst
little less least
far farther/further farthest/furthest

By their nature, some adjectives cannot be compared because they are already at their highest extent or degree. These adjectives are perfect, unique, excellent, outstanding, etc.