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

After initially qualifying for the 2020 Summer Olympics in Tokyo, she was later disqualified after testing positive for THC during a post-race drug test. —David Matthews, New York Daily News, 30 Jan. 2026

In 2021, Richardson tested positive for THC, which is the chemical in marijuana, during a post-race drug test, giving her a 30-day suspension and ineligibility for the Tokyo Olympics. —Ingrid Vasquez, PEOPLE, 30 Jan. 2026

And at the federal level, Congress is pressing pause on a new hemp definition that would have reshaped THC compliance nationwide. —Alonzo Martinez, Forbes.com, 30 Jan. 2026

In 2021, Richardson accepted a one-month competition ban after testing positive for THC, the active ingredient in marijuana, and was omitted from the Tokyo Olympics roster. —Sportsday Staff, Dallas Morning News, 29 Jan. 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