Cannabis strains are either pure or hybrid varieties of the plant genus Cannabis, which encompasses the species Cannabis sativa, Cannabis indica, and Cannabis ruderalis.
Varieties are developed to intensify specific characteristics of the plant, or to differentiate the strain for the purposes of marketing or to make it more effective as a drug. Variety names are typically chosen by their growers, and often reflect properties of the plant such as taste, color, smell, or the origin of the variety. The Cannabis strains referred to in this article are primarily those varieties with recreational and medicinal use. These varieties have been cultivated to contain a high percentage of cannabinoids. Several varieties of cannabis, known as hemp, have a very low cannabinoid content, and are instead grown for their fiber and seed.