The quick answer

Use a superlative adjective — usually adjective + -est, or the most + adjective — to compare three or more things and pick the extreme one. Say the biggest animal, not the more big animal.

The rule

A superlative always needs the before it, and it compares one thing with a whole group, not just two things. Short adjectives (one syllable, and some two-syllable ones) add -est: tall → the tallest. A single vowel plus consonant doubles the consonant: big → the biggest. A final -y changes to -i: heavy → the heaviest. Longer adjectives use the most instead of an ending: dangerous → the most dangerous. A few common adjectives are irregular: good → the best, bad → the worst.

Form

Examples

• The blue whale is the biggest animal on Earth.
• The cheetah is the fastest land animal.
• The giraffe is the tallest animal in the world.
• The mosquito is the most dangerous animal of all.
• The dog is the best pet of all.

Common mistakes

• ❌ She is tallest in the class. → ✅ She is the tallest in the class. A superlative always needs the before it.
• ❌ This is the bigest animal here. → ✅ This is the biggest animal here. Big doubles the final consonant before -est.
• ❌ He is the most tall boy. → ✅ He is the tallest boy. Short adjectives use -est, not the most.
• ❌ She is the goodest cook. → ✅ She is the best cook. Good is irregular; the superlative is best.