Sinus Means a Curve or Fold
A sinus is an air cavity in the skull. The Latin word meant a bay or fold in cloth, and it also produced the word sine.
A sinus is an air-filled cavity in the bones of the skull, connected to the nose. Latin *sinus* meant a curve, a fold in a garment, or a bay in a coastline — anything that curves inward. The mathematical *sine* comes from the same word by a chain of translation errors: Sanskrit *jya*, a bowstring, was transliterated into Arabic, misread as *jaib*, a fold or bosom, and then translated into Latin as *sinus*. Humans have four pairs of paranasal sinuses.
- A skull cavity. *Blocked sinuses.*
- Sinusitis — inflammation. *Sinusitis.*
- Sine — the trigonometric function. *Sine.*
- Latin — *sinus*, a fold or bay. *The source.*
- Paranasal — beside the nose. *Paranasal sinuses.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | sinus | A sinus. |
| Plural | sinuses | Sinuses. |
| Adjective | sinusitis | Sinusitis. |
| Related | sine | Sine. |
| Latin | sinus | A fold. |
- His sinuses were blocked for weeks.Medicine.
- Sinus meant a fold in cloth.Etymology.
- Sine came from a mistranslation.Maths.
How sine got its name
- Sanskrit *jya-ardha*, half a bowstring, shortened to *jya*
- Arabic transliterated it as *jiba*, written without vowels
- Readers saw *jaib*, meaning a fold or opening in a garment
- Latin translators rendered that as *sinus*, a fold
- English took sine from the Latin, four languages from the bowstring
Latin *sinus*, a curve, fold or bay, of uncertain further origin.
Why is the sine function called that?
Through a chain of translation: a Sanskrit word for bowstring was transliterated into Arabic, misread as a word meaning fold, and translated into Latin as sinus.
How many sinuses do humans have?
Four pairs of paranasal sinuses: frontal, maxillary, ethmoid and sphenoid.