semantics
/ suh-MAN-tiks /
Semantics is the study of meaning in language — what words and sentences actually say, as opposed to how they sound or how they're built. If you point at a chair and ask "What does this word mean?", you're already doing semantics: you're asking what idea the noise "chair" reaches out and grabs in the world.
It matters because meaning is where language does its real work, and it splits into two layers. Word meaning asks why "dog" picks out furry barking animals and not the moon. Sentence meaning asks how those pieces combine: "the dog bit the man" and "the man bit the dog" use the very same words, yet mean opposite things — so meaning clearly lives in the arrangement too, not just the parts.
A common mix-up is to lump semantics together with grammar. But a sentence can be perfectly grammatical and still mean nothing sensible — "colorless green ideas sleep furiously" breaks no rules of structure, yet semantically it's nonsense. Meaning and well-formedness are two different questions, and semantics is the one about meaning.
"The dog bit the man" vs. "The man bit the dog" — same words, opposite meanings.
Meaning depends on arrangement, not just the words themselves.
The word comes from the Greek sēmantikós, "significant," from sēma, "sign" — the same root behind "semaphore." It entered linguistics through French sémantique, coined by Michel Bréal in 1883.