Hemp and marijuana are the same plant species: Cannabis sativa. They are legally distinguished based on their total delta-9-Tetrahydrocannabinol (THC) content. Total THC includes delta-9-THC and the precursor THCa, the psychoactive compounds associated with ‘getting high.’
Hemp is Cannabis sativa with a total THC content that does not exceed 0.3 percent by dry weight, while marijuana is Cannabis sativa with a total THC (THC + THCa) content greater than 0.3 percent by dry weight, while marijuana is Cannabis sativa with a total THC content greater than 0.3 percent. The 0.3 percent total THC threshold is defined by state and federal laws.
Hemp is used for fiber, seed, oil, non-THC cannabinoids, and various other derivatives. Some hemp varieties can be high in cannabidiol (CBD) and other cannabinoids. Hemp and marijuana may also be called Cannabis indica or Cannabis ruderalis, which are biologically-synonymous terms for Cannabis sativa. More accurately, indica and ruderalis denote subspecies.