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

As a result of the allegations, Derry was subjected to a drug test and ultimately tested positive for THC and cocaine. —Patrick Damp, CBS News, 8 June 2026

Whether the weed was smoked or taken in edible form is probably also important; THC immediately affects the brain when smoking while edibles take time for the body to metabolize. —Shoshi Parks, Popular Science, 3 June 2026

And cocaine isn’t the only issue, either; trace levels of THC, MDMA, methadone and antidepressants have also been detected in aquatic ecosystems around the world. —Scott Travers, Forbes.com, 30 May 2026

Hemp is a variety of cannabis with a negligible level of the psychoactive compound THC. —Phil Diehl, San Diego Union-Tribune, 27 May 2026

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