Practice Makes Perfect: Exploring Grammar - Muschla Gary Robert 2010

Comparing with adjectives
Adjectives

Many adjectives have three forms. These forms are used when nouns or pronouns are compared.

✵ To compare two things, add -er to most adjectives. To compare three or more things, add -est.

✵ For adjectives that end in -e, drop the final -e and add -er or -est.

✵ For adjectives that end with a consonant and -y, change the -y to -i and add -er or -est.

✵ For adjectives of one syllable that end with a single vowel and a consonant, double the consonant and add -er or -est.

Here is an example of comparing with adjectives.

The brown puppy is big.

The white puppy is bigger than the brown puppy.

The black puppy is the biggest puppy of the litter.