A soluble colouring material that chemically bonds with or is absorbed into the material it colours, such as fabric.
Unlike a pigment, a dye dissolves into the substrate rather than remaining as discrete suspended particles — this generally makes dyes suited to fabric and pigments suited to paint, though some materials use both.
'Dye' and 'pigment' are often used interchangeably in everyday speech, but they are physically different (see pigment).
Indigo and cochineal are historically significant dyes — see the pigments & dyes section for structured records.
Understanding pigment vs dye explains why some historical colourants suited textiles and others suited paint or ink.