sinus

sinus

Inherited from Proto-Italic *sinus, from Proto-Indo-European *sinos. Akin to Albanian gji (“breast, bosom”).

The mathematical sense “chord of an arc, sine” was introduced in the 12th century by Gherardo of Cremona as a semantic loan from Arabic جِيبَ(jība, “chord, sine”) (ultimately a loan from Sanskrit ज्या (jyā, “bowstring”)) by confusion with جَيْب (jayb, “bosom, fold in a garment”).

Pronunciation

• (Classical Latin) IPA^(key): [ˈsɪ.nʊs]
• (modern Italianate Ecclesiastical) IPA^(key): [ˈsiː.nus]

Noun

sinus m (genitive sinūs); fourth declension

1. (chiefly poetic) a bent surface; a curve, fold, hollow
2. (literal) the hanging fold of a toga over the breast; a pocket, lap

   Synonym: gremium

   1. (transferred sense)
      1. a purse, money (which was carried in the bosom of the toga)
      2. (poetic) a garment
      3. the bosom, breast

         Synonym: pectus

   2. (figurative)
      1. the bosom for love, protection, asylum
      2. the interior, inmost part of a thing
      3. a power, possession of someone
      4. a hiding place, place of concealment; a secret feeling
3. a gulf, bay, bight
   1. the land lying on or a point of land that helps to form a gulf
   2. a basin, hollow, valley
   3. (Medieval Latin) a fjord
4. (Medieval Latin, mathematics) the chord of an arc; a sine