Meaning

noun ratio of the length of the side opposite the given angle to the length of the hypotenuse of a right-angled triangle

originEtymology tree Proto-Indo-European *sinos Proto-Italic *sinus Latin sinusbor. English sine Borrowed from Latin sinus (“curve, bend; bosom”), a translation of Arabic جَيْب (jayb, “bosom”), a misidentification of the notation جيب (j-y-b), written without vowel diacritics, standing for Arabic جِيبَ (jība, “sine”), in turn from Sanskrit ज्या (jyā, “sine, chord, bowstring”) through the similar…

Etymology from Wiktionary, CC BY-SA 3.0