A synonym is a word that means the same thing, or nearly the same thing, as another word. Happy and joyful are synonyms. Big and large are synonyms. Smart and intelligent are synonyms.

Synonyms give you choices in how to express yourself. If you've already used the word said three times in a story, you might switch to replied, answered, or exclaimed. These synonyms keep your writing from sounding repetitive while still conveying the same basic meaning.

Most synonyms aren't perfectly identical, though. They carry slightly different feelings or fit better in different situations. Angry and furious are synonyms, but furious suggests stronger emotion. House and home are synonyms, but home feels warmer and more personal. Smell and stench both refer to odors, but stench specifically means a bad smell. Good writers choose synonyms carefully to express exactly what they mean.

The opposite of a synonym is an antonym, which is a word with the opposite meaning, like hot and cold or fast and slow.