ash, in botany, any plant of the genus Fraxinus of the family Oleaceae (olive family), trees and shrubs mainly of north temperate regions. The ashes are characterized by small clusters of greenish flowers and by fruits with long "wings" to aid in wind dispersal. The most valuable of the species used for hardwood timber is the white ash (F. americana), ranging from Nova Scotia to Minnesota and Texas. Its strong, durable wood is used for sporting goods, furniture, tool handles, and oars. The bark of the blue ash (F. quadrangulata) yields a blue dye; the Mediterranean flowering ash (F. ornus) is the source of commercial manna. The name flowering ash is also applied to a shrubby species (F. cuspidata) of the California canyon chaparral and to the fringe tree (genus Chionanthus of the same family) of North America and China. The mountain ash and prickly ash are not true ashes. Ashes are classified in the division Magnoliophyta, class Magnoliopsida, order Scrophulariales, family Oleaceae.
ash, in chemistry, solid residue of combustion. The chemical composition of an ash depends on that of the substance burned. Wood ash contains metal carbonates (e.g., potassium carbonate) and oxides formed from metals originally compounded in the wood. Coal ash usually has a high content of minerals and is sometimes contaminated with rock; during combustion the mineral matter may become partially fused, forming cinders or clinker. Bone ash is largely made up of calcium phosphate. Seaweed ash (called kelp or varec) contains sodium carbonate, potassium carbonate, and iodine that can be extracted. Fly ash is very fine ash produced during the combustion of many materials.
Ash may refer to:

Products of fire, incineration or combustion


  • Ash tree, any tree of the genus Fraxinus, or the wood from those trees
  • Mountain Ash, any of several other trees
  • Prickly Ash, any of several species of the genus Zanthoxylum


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