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

While most research into cannabis compounds has focused on THC and CBD, CBC is emerging as a potentially important but underexplored cannabinoid. —New Atlas, 10 Jan. 2026

ProPublica reviewed cutoff levels used to confirm the presence of common drugs, including opiates, meth, THC and cocaine, as cited in court records, labs’ contracts with government agencies and scientific journals, as well as in interviews with toxicologists. —Lucas Waldron, ProPublica, 6 Jan. 2026

Panks, who with his wife started Deafining Cannabis to develop sign language related to the plant, said that instead of focusing on high THC, users should look more into the effects of cannabis terpenes, the compounds that help give cannabis and other plants their distinctive effects. —Robert McCoppin, Chicago Tribune, 5 Jan. 2026

Seven businesses, including gas stations and convenience stores, in Maywood were shut down for illegally selling tobacco and THC products to minors, the village announced over the weekend. —Jeramie Bizzle, CBS News, 4 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