A tartan is a pattern consisting of crisscrossed horizontal and vertical bands in multiple colours. Tartans originated in woven cloth, but are now used in many other materials. Tartan is particularly associated with Celtic countries, especially Scotland. Scottish kilts almost always have tartan patterns. (Tartan is also known as plaid in North America, but in Scotland this word means a tartan cloth slung over the shoulder or a blanket.)

A Tartan is made with alternating bands of coloured (pre-dyed) threads woven as both warp and weft at right angles to each other. The weft is woven in a simple twill, two over - two under the warp, advancing one thread each pass. This forms visible diagonal lines where different colours cross, which give the appearance of new colours blended from the original ones. The resulting blocks of colour repeat vertically and horizontally in a distinctive pattern of squares and lines known as a sett.