means a mathematical object that generalizes scalars, vectors, and matrices to represent quantities with multiple directional components, transforming in a consistent way under changes of coordinates.

from From Latin 'tendere,' to stretch — the same root that gives us 'tension' and 'tense.' The word entered anatomy first, naming muscles that stretch or tighten (a 'tensor' muscle pulls something taut). In the 1840s the mathematician William Rowan Hamilton borrowed the term for the magnitude that 'stretches' a quantity in his quaternion work; later the word was repurposed by Woldemar Voigt and others for the broader multi-directional objects we know today. So beneath all the indices and directions sits a humble idea: something that pulls and stretches.