Sinus

How to spell sinus

5 letters · 2 syllables

How to pronounce sinus

Say the part in capitals loudest.

What does sinus mean?

1. nounAn air-filled cavity in the bones of the face and skull, or any similar hollow channel in the body.

Sinus in a sentence

• The cold left her with a blocked sinus and a constant headache.

• The surgeon explained that an infected sinus was causing the pressure behind his eyes.

Where does sinus come from?

Language of origin: Latin

The word comes straight from the Latin sinus, which literally meant a curve, a fold, a bay, or a hollow; it was the same word the Romans used for the loose draped fold of a toga where someone could tuck their hands or carry small items. From that idea of a curved hollow it was a natural step to anatomical use, naming the air-filled cavities and curved channels inside the body, especially those in the bones of the face and skull. Medical Latin of the 1500s and 1600s adopted it for these recesses, and English took it over wholesale by the early seventeenth century without changing the spelling. The same root also gave mathematics its 'sine', through a winding history of mistranslation, which is why the spellings look so alike. Because the word kept its bare Latin form, the trap for a writer is the unstressed second syllable, which sounds like a vague 'uss' yet is written -us, not -ous or -is.

How the word is built

• sinus (Latin: a bend, fold, or hollow), used unchanged as an English noun