Posting for my own reference

I was losing this part of my grammar beaten into me by nuns, so had to get a reminder.

The comparative forms of most adjectives, however, are formed by adding the suffixes
-er and -est, or by placing the words more and most in front of the positive form.

RULES FOR FORMING COMPARATIVES:
1. One syllable words form the comparative by adding -er and -est:
brave, braver, bravest
small, smaller, smallest
dark, darker, darkest.

2. Two-syllable words that end in -y, -le, and -er form the comparative by adding -er and -est:
pretty, prettier, prettiest
happy, happier, happiest
noble, nobler, noblest
clever, cleverer, cleverest

3. Words of more than two syllables form the comparative with more and most:
beautiful, more beautiful, most beautiful.
resonant, more resonant, most resonant