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

People who consumed edibles laced with tetrahydrocannabinol, or THC, showed signs of early cardiovascular disease similar to tobacco smokers. —Cnn.com Wire Service, Mercury News, 18 June 2025

Hemp generally has very low amounts of intoxicating compounds like delta-9 THC, the main intoxicating compound in cannabis. —Dan Belson, Baltimore Sun, 16 June 2025

That test registered positive for THC, the active ingredient in marijuana, the union said. —Graham Rayman, New York Daily News, 13 June 2025

The brownie came back positive for THC, Watts said. —Elizabeth Hernandez, Denver Post, 13 June 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