Superlative adjectives are words like biggest, smallest, hungriest, most peculiar, and least desirable. Use them only when you are ranking three or more things. Use comparative adjectives — like bigger, smaller, hungrier, more peculiar, less desirable — when you are comparing two things.

This rule doesn’t apply to comparisons with than:

As for whether to give an adjective an -er or -est ending (as in tastier, the tastiest) or use more or less or the most or the least (as in more delicious, the most delicious), use the ending if you know the adjective has one. Most short adjectives do. The comparative and superlative forms of longer adjectives, though, usually consist of more or less or the most or the least plus the base form: more nutritious, the most nutritious.

If you’re not sure how to form the comparative or superlative for a particular adjective, check a dictionary. If it doesn’t list -er and -est forms for the adjective, then use the additional word or words.