<unk> s are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers, though also by some insects such as swallowtail butterflies, which emit<unk> s from their osmeterium. They are the major components of resin, and of turpentine produced from resin. The name<unk> " is derived from the word "turpentine".
When<unk> s are modified chemically, such as by oxidation or rearrangement of the carbon skeleton, the resulting compounds are generally referred to as<unk> ids.  Some authors will use the term<unk>  to include all<unk> ids.<unk> s and<unk> ids are the primary constituents of the essential oils of many types of plants and flowers.  Essential oils are used widely as natural flavor additives for food, as fragrances in perfumery, and in traditional and alternative medicines such as aromatherapy.  Synthetic variations and derivatives of natural<unk> s and<unk> ids also greatly expand the variety of aromas used in perfumery and flavors used in food additives.  Vitamin A is an example of a<unk> .
Terpene
Diol
Haloalkane
Polycyclic aromatic hydrocarbon
Cycloalkane
Halide
Indole alkaloid
Oxoacid