COMMONLY USED TERMS

Cannabis
Cannabis is a species of plant that makes a substance full of compounds called cannabinoids. These compounds can produce a drug-like effect in the body.
Marijuana

The flowering tops of the cannabis plant.

Cannabinoid
Compounds that can produce a drug-like effect in the body. CBD (cannabidiol) and THC (tetrahydrocannabinol) are the most common cannabinoids.
THC

Tetrahydrocannabinol, or THC, is the most well-known phytocannabinoid. It can have psychoactive effects and produce a “high,” but not necessarily. Its medical uses include pain relief, insomnia, and more.

CBD
Cannabidiol or CBD is a phytocannabinoid that does not have psychoactive effects. It has been linked to helping with pain relief, seizure control, inflammation, and more.
Endocannabinoid

A cannabinoid produced by the human body.

Phytocannabinoid

A cannabinoid produced in nature, by the cannabis plant.

Endocannabinoid system

The regulatory system in the human body that deals with memory, hunger, emotions, stress, and immune function. Discovered in Israel by Raphael Mechoulam in 1991.

Hemp
Hemp is a strain of the cannabis plant that is grown specifically for its industrial uses, like the creation of rope, paper, and clothing. It is not used medicinally or recreationally. It has very little THC.
Strain

A strain is a variety of cannabis plant. Different strains have different types of cannabinoids, and different levels of those cannabinoids. They therefore produce different effects in the body.

Hybrid
Hybrid refers to a plant that is a cross between one or more strains.
Flowers

Flowers are the hairy, sticky parts of the cannabis plant. They are harvested and dried, and can be smoked directly.

Edibles
Edibles are ingestible food products that have been infused with cannabis extracts. The active components of edible products take longer to take effect, because they must be absorbed through the digestive system.
Vaporizing
Vaporizing uses a device to heat flowers or infused oils to a temperature that produces a vapor, which is then inhaled.
Tincture/liquid extract

A form of medicine that can be taken sublingually or internally, without smoking or vaporizing.  Generally made from diluting cannabis oil or directly infusing cannabis into a carrier oil. 

Dabbing

A method of vaporizing cannabis oil on a hot surface, usually through a water pipe.

Dispensary
A dispensary is a general term used to refer to any location where cannabis can be legally purchased, whether for medical or recreational uses.

While not used as much anymore, sativa/indica can be a useful shorthand to refer to the effects of cannabis strains (varietals):

Sativa

Originating in tropical climates, sativas are thought to be more energizing. They typically have higher THC and lower CBD. They are associated with daytime use.

Indica

Originating in mountainous highlands, these plants are associated with being more calming. They are considered best for nighttime use. They typically have lower THC and higher CBD. 

Hybrid

A genetic mixture of indica and sativa, describing most strains available today. These can take the best traits of multiple plants to produce desired effects.