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

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

Wegovy HD is a once-weekly injection that contains 7.2 milligrams of active ingredient semaglutide, offering the highest weight-loss of any Wegovy injection so far, the company said.

From The Wall Street Journal • Apr. 7, 2026

Hansen then described the translunar injection burn -- a maneuver that brought Orion within 200 kilometers of Earth before swinging around onto a new course for the Moon.

From Barron's • Apr. 4, 2026

The images were taken after the crew successfully completed a trans-lunar injection burn in the early hours of Friday.

From BBC • Apr. 3, 2026

Finally, when the sky grew dark, Sister Gladys gave her an injection to make her sleep and to lessen the pain of the broken wrist.

From "A Girl Named Disaster" by Nancy Farmer

Related Words

• dose
• needle