Trigonometry · a Light

Sine is a mistranslation of a misread Arabic word

Indian astronomers worked with the half chord of an arc and called it jya. When their tables were translated into Arabic the word was carried across by sound as jiba, which means nothing in Arabic. Written without vowels, those same letters spell jayb, which means a fold, or the opening at the breast of a garment where things are kept. Later readers naturally read it that way, because it was a real word. When the Arabic was translated into Latin in twelfth century Spain, the translator rendered the meaning he found, and jayb became sinus, the Latin for a fold or a bay. English shortened that to sine. The function is Indian, the name is an accident, and the tangent began separately as the length of a shadow.

India to Baghdad to Toledo · one word's route