degree of comparison

Adjectives of one syllable

Adjectives of one syllable add -er and -est.
Adjectives ending on 'e' just add -r and -st.
Some adjectives double the final consonant.

Adjective Comparative Superlative
small
warm
old
nice
big smaller
warmer
older
nicer
bigger smallest
warmest
oldest
nicest
biggest

2. Adjectives of two syllables

Some adjectives of two syllables add -er and -est.
Adjectives ending in 'y' use -ier and -iest.
Adjectives ending in -ful, -less, -ing, -ed use more and most.
Some other adjectives of two syllables use more and most (modern, famous, normal, correct, ...).

Adjective Comparative Superlative
narrow
happy
useful
boring
modern narrower
happier
more useful
more boring
more modern narrowest
happiest
most useful
most boring
most modern

3. Adjectives of three or more syllables

Adjectives of three or more syllables use more and most.

Adjective Comparative Superlative
beautiful
dangerous
exciting more beautiful
more dangerous
more exciting most beautiful
most dangerous
most exciting

4. Irregular adjectives

You will have to learn these by heart.

Adjective Comparative Superlative
good (well)
bad
little
much, many
far
late
old better
worse
less
more
farther, further
later
older, elder best
worst
least
most
farthest
last, latest
older, oldest