injection

American  

[in-jek-shuhn] / ɪnˈdʒɛk ʃən /

noun

1. the act of injecting.

2. something that is injected.

3. a liquid injected into the body, especially for medicinal purposes, as a hypodermic or an enema.

4. state of being hyperemic or bloodshot.

5. Mathematics. a one-to-one function.

6. Also called insertion.  Aerospace. the process of putting a spacecraft into orbit or some other desired trajectory.

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injection British  

/ ɪnˈdʒɛkʃən /

noun

1. fluid injected into the body, esp for medicinal purposes

2. something injected

3. the act of injecting

4. 1. the act or process of introducing fluid under pressure, such as fuel into the combustion chamber of an engine

   2. ( as modifier )

      injection moulding

5. maths a function or mapping for which f( x ) = f( y ) only if x = y See also surjection bijection

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injection Scientific  

/ ĭn-jĕk′shən /

1. A substance that is introduced into a organism, especially by means of a hypodermic syringe, as a liquid into the veins or muscles of the body.

2. A function that maps each member of one set (the domain) to exactly one member of another set (the range).

3. Compare bijection surjection

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Other Word Forms

• injective adjective
• postinjection adjective
• reinjection noun
• superinjection noun

Etymology

Origin of injection

First recorded in 1535–45, injection is from the Latin word injectiōn- (stem of injectiō ). See inject, -ion

Explanation

An injection is a shot, or a dose of medicine given by way of a syringe and a needle. When you get jabbed in the arm with a tetanus vaccine, that's an injection. The medical kind of injection forces a small amount of a drug under the skin or directly into a muscle. Other injections are similar in that they involve a liquid being forced by pressure, like the fuel injection in a car, which pushes gasoline directly into the engine. Since the 1600s, injection has been used to mean "forcing a fluid into a body," from the Latin inicere, "to throw in" or "to throw on."

Example Sentences

Although Lilly has been a later entrant to the weight-loss drug market than Novo, it nonetheless has overtaken its competitor in recent months, as sales of Lilly’s Zepbound injection continue to pull ahead of Wegovy.

From Barron's • Apr. 15, 2026

"They should keep the threshold for injection practice very high. Only give injections for life-threatening illnesses. For mild to moderate illnesses, use oral medication."

From BBC • Apr. 13, 2026

Until the Food and Drug Administration approved Wegovy HD last month, the highest available dose of Novo’s GLP-1 injection was 2.4 mg.

From MarketWatch • Apr. 8, 2026

If developed for human use, this type of male contraceptive could be delivered as an injection given every three months or possibly as a patch to maintain effectiveness, Cohen said.

From Science Daily • Apr. 7, 2026

To everyone’s relief, after about twenty minutes the injection and extra oxygen revived Pittman and she was able to resume the descent under her own power.

From "Into Thin Air" by Jon Krakauer

Related Words

• dose
• needle