THC

noun

ˌtē-(ˌ)āch-ˈsē 

: either of two physiologically active isomers C₂₁H₃₀O₂ from hemp plant resin

especially : one that is the chief intoxicant in marijuana

When a person tokes, eats or vapes cannabis, a wave of THC, or tetrahydrocannabinol, washes into the brain.

—Laura Sanders

THC, the main chemical component of marijuana, has been shown to reduce nausea and increase appetite in chemotherapy patients.

—Andrew Weil

THC disappears from blood quickly as it is absorbed in the brain, making blood tests a more reliable measure of recent use but not a great correlate of impairment.

—Eliza Gray

Examples of THC in a Sentence

Recent Examples on the Web

Subsequent testing confirmed the presence of THC, the psychoactive compound in marijuana. —Amanda Castro, MSNBC Newsweek, 19 Sep. 2025

The research that is now available shows that cannabinoid receptors are present in the fetus as early as 5 weeks, and the main psychoactive component of cannabis, THC, can cross the placenta and transfer into breast milk – and that exposure is associated with risks of adverse outcomes. —Deidre McPhillips, CNN Money, 18 Sep. 2025

The suit notes that the product’s labeling contained no mention of THC. —Kansas City Star, 18 Sep. 2025

The drug, currently called Ver-01, packs enough low levels of cannabinoids (including THC) to relieve pain, but not so much that patients get high. —Amy Feldman, Forbes.com, 17 Sep. 2025

Word History

Etymology

tetrahydrocannabinol

First Known Use

1967, in the meaning defined above

Medical Definition

THC

noun

ˌtē-ˌāch-ˈsē 

: either of two physiologically active isomers C₂₁H₃₀O₂ that occur naturally in hemp plant resin or are synthetically prepared:

a

: one that is the chief intoxicant in marijuana and is used medicinally

called also delta-9-tetrahydrocannabinol, delta-9-THC

see dronabinol

b

: one that is present in marijuana only in minute quantities