We usually add –er and –est to one-syllable words to make comparatives and superlatives:
old
older
oldest
long
longer
longest
If an adjective ends in –e, we add –r or –st:
nice
nicer
nicest
large
larger
largest
If an adjective ends in a vowel and a consonant, we double the consonant:
big
bigger
biggest
fat
fatter
fattest
If an adjective ends in a consonant and –y, we change –y to –i and add –er or –est:
happy
happier
happiest
silly
sillier
silliest
We use more and most to make comparatives and superlatives for most two syllable adjectives and for all adjectives with three or more syllables:
careful
more careful
most careful
interesting
more interesting
most interesting
However, with these common two-syllable adjectives, you can either add –er/–r and –est/–st or use more and most:
common
cruel
gentle
-
handsome
likely
narrow
-
pleasant
polite
simple
stupid
He is certainly
handsomer than his brother.
His brother is handsome, but he is
more handsome.
She is one of the
politest people I have ever met.
She is
the most polite person I have ever met.
The adjectives good, bad and far have irregular comparatives and superlatives:
good
better
best
bad
worse
worst
far
farther/further
farthest/furthest