Dye
A coloured substance that dissolves and bonds with fibres, used to colour cloth, leather and paper.
Also: dyestuff
A dye is dissolved in water or another liquid and taken up by a material, usually textile fibre, so that the colour becomes part of it. Until the mid 19th century all dyes came from nature: plants such as indigo and madder, insects such as cochineal and lac, and sea snails. Almost all dyes used today are synthetic. Different fibres need different dyes; what colours wool well may not hold on cotton. Many dyes need a helper chemical, called a mordant, to fix them so that they do not wash out.