Adjectives and adverbs ending in -er or modified by the word more compare two items and ate known as comparative.
Adjectives or adverbs ending in -est or modified by the word most compare three or more items and are known as superlative.
Normally, -er and -est are added to one-syllable words.
-er and -est are added to two-syllable words unless the new word sounds awkward.
Correct: Everest is taller than Annapurna.
Incorrect: Everest is the taller of the three peaks.
(Three or more requires superlative.)
Correct: Annapurna is the tallest of the three peaks.
Correct: fairer prettier handsomestAwkward: famousest readier
Correct: most famous more ready
Use the modifiers more or most with all root words longer than two syllables as well as with two syllable words that sound awkward. Always use more or most with adverbs that end in -ly.
Incorrect: beautifuller smoothliestCorrect: more beautiful most smoothly
Correct: friendliest beastliest (adjectives, not adverbs)
Less and least form comparisons of a lesser degree in a similar manner. Less (sometimes lesser) is used when comparing two items, least with three or more.
Paul had less money than Sally
Ben, Sally and John went to the fair. Sally had the least amount of money.
Peter could walk home in the rain or spend his money on a bus ticket. Because he was saving up for new football boots he chose walking as the lesser of two evils.