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

Seven products contained undisclosed active ingredients such as caffeine, kava extract (a legal herbal supplement with antianxiety and hallucinogenic effects) and cannabis extract (including the plant’s main psychoactive ingredient, tetrahydrocannabinol, or THC). —Allison Parshall, Scientific American, 11 Sep. 2025

In Arizona, medical cannabis patients cannot be convicted solely based on THC presence, but prosecutors can still argue impairment. —Andrew Yockey, The Conversation, 11 Sep. 2025

The order also directs the agency to require identification of all customers purchasing THC products and to establish rules to revoke the permits of retailers who fail to comply with the requirement. —A.j. Herrington, Forbes.com, 10 Sep. 2025

The researchers studied how THC affected egg maturation, gene activity, chromosomes, and spindle formation (the machinery that equally divides the chromosomes in a cell). —New Atlas, 10 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