Languages rarely keep two words with exactly identical use. A synonym is a word that shares substantially the same meaning as another, though total synonymy is rare once register, collocation, and connotation are considered.

Near-synonyms let speakers fine-tune style and attitude. Thesauruses group synonyms to support writing, but uncritical substitution can produce awkward prose. Lexical semantics studies how synonym sets divide subtle semantic and pragmatic space.

Learners collect synonyms to expand expressive range. Historical change can push former synonyms apart or bring different words into closer competition. Careful synonym choice is a hallmark of precise writing.

• Word with substantially similar meaning to another
• Usually differs in register or connotation
• Listed in thesauruses for writers and learners
• Rarely identical in all contexts of use