Terpenes are a large and diverse class of organic compounds produced by a variety of plants, and by some insects. They typically are characterized by a strong odor and help protect the plants that produce them by deterring herbivores and by attracting predators and parasites of herbivores.
The name "terpene" is derived from the word "terpentine", an obsolete form of the word "turpentine". Terpenes are also major biosynthetic building blocks. Steroids for example, are derivatives of the triterpene squalene.
Terpenes and terpenoids are the primary constituents of essential oils of many types of medicinal plants and flowers. Essential oils are used widely as fragrances in perfumery, medicine and alternative medicines such aromatherapy. Synthetic variations and derivatives of natural terpenes and terpenoids also greatly expand the variety of aromas used in perfumery and flavors used in food additives. Terpenes are also major constituents of Cannabis plants, which contain at least 120 identified compounds. It is believed that these aromatic compounds might modulate the effect of cannabinoids in the body, enhancing their properties. This phenomenon is usually known as entourage effect.