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

After finding the primary injection line, "the team continued to follow the protocol, but could not find another suitable vein", the corrections department said in a statement.

From BBC • May 21, 2026

Morningstar lowers its fair value estimate by 6% to S$6.30, reflecting near-term earnings pressure and Air India’s capital injection.

From The Wall Street Journal • May 19, 2026

That means those patients can maintain their weight even if they get an injection every two weeks or so rather than every week.

From MarketWatch • May 18, 2026

According to the MMWR, investigators said the cooling tower had malfunctioned, leading to either very little or no injection of chemicals that would prevent bacterial growth.

From Los Angeles Times • May 18, 2026

Using a second needle, Southam tattooed a tiny speck of India ink next to the small bump that formed at the HeLa injection site.

From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot

Related Words

• dose
• needle