Δ9-Tetrahydrocannabinol (THC): a crystalline compound that is the main active
ingredient of cannabis.

α-Terpinolene: a type of terpene mixture made from gum turpentine.

α-Humulene: naturally occurring monocyclic sesquiterpene. It is found in the essential oils of Hops. It also contributes to the characteristic aroma of cannabis where it is present in the essential oil of the plant.

Acid: a bitter or sharp substance, having a pH less than 7 e.g. soil that has a pH of less
than 7.5 is considered to be acidic.

Active carbon: virginal activated carbon which is porous to allow absorption of particles.

Active ingredient: the substance in a drug that is pharmaceutically active.

Aeration: providing air or oxygen to soil and roots.

Aids: acquired immune deficiency syndrome, a disease in which there is a severe loss of the body’s cellular immunity, greatly lowering the resistance to infection and malignancy.

Air stones: mainly used in fish tanks connected to an air pump to facilitate aeration of
water.

Albumin: a simple form of protein that is soluble in water and coagulable by heat, such
as found in egg white, milk, and in particular, blood serum.

Alcoholism: addiction to the consumption of alcoholic liquor; alcohol dependency.

Algae: collective name given to plants that grow extensively in water.

Algaecides: any substance that kills algae.

Allergen: a substance that causes an allergic reaction.

Alpha male: lead male, top of class or breed.

Amino acid: a simple organic compound containing both a carboxyl and an amino.

Amino acids occur naturally in plant and animal tissues and form the basic constituents of proteins. There are about 20 common amino acids of which the simplest is glycine.

Analgesia: medication that acts to relieve pain.

Analgesic: action to relieve pain usually with the use of drugs.

Androgynous: having male and female characteristics.