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• act
  act

  noun

  anything done, being done, or to be done; deed; performance.
• ACT
  ACT

  a standardized college admissions test developed by ACT, Inc., measuring English, mathematics, reading, and science skills: originally an abbreviation of American College Testing/American College Test.
• act.
  act.

  abbreviation

  acting.

act

¹ American  

[akt] / ækt /

noun

• acts
  plural

1. anything done, being done, or to be done; deed; performance.

   a heroic act.

   Synonyms:

   accomplishment, transaction, achievement, exploit, feat

2. the process of doing.

   caught in the act.

3. a formal decision, law, or the like, by a legislature, ruler, court, or other authority; decree or edict; statute; judgment, resolve, or award.

   an act of Congress.

4. an instrument or document stating something done or transacted.

   Synonyms:

   record

5. one of the main divisions of a play or opera.

   the second act of Hamlet.

6. a short performance by one or more entertainers, usually part of a variety show or radio or television program.

   Synonyms:

   routine, turn

7. the personnel of such a group.

   The act broke up after 30 years.

8. false show; pretense; feint.

   The politician's pious remarks were all an act.

9. Philosophy. (in scholasticism)

   1. activity in process; operation.

   2. the principle or power of operation.

   3. form as determining essence.

   4. a state of realization, as opposed to potentiality.

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verb (used without object)

• acts,
  present (3rd person singular)
• acted,
  past participle,  past
• acting
  present participle

1. to do something; exert energy or force; be employed or operative.

   He acted promptly in the emergency.

   Synonyms:

   play, work, function, perform

2. to reach, make, or issue a decision on some matter.

   I am required to act before noon tomorrow.

   Synonyms:

   play, work, function, perform

3. to operate or function in a particular way; perform specific duties or functions.

   to act as manager.

   Synonyms:

   play, work, function, perform

4. to produce an effect; perform a function.

   The medicine failed to act.

   Synonyms:

   play, work, function, perform

5. to behave or conduct oneself in a particular fashion.

   to act well under all conditions.

6. to pretend; feign.

   Act interested even if you're bored.

7. to perform as an actor.

   He acted in three plays by Molière.

8. to be capable of being performed.

   His plays don't act well.

9. to serve or substitute (usually followed byfor ).

   In my absence the assistant manager will act for me.

verb (used with object)

• acts,
  present (3rd person singular)
• acted,
  past participle,  past
• acting
  present participle

1. to represent (a fictitious or historical character) with one's person.

   to act Macbeth.

   Synonyms:

   play

2. to feign; counterfeit.

   to act outraged virtue.

3. to behave as.

   He acted the fool.

   Synonyms:

   play

4. Obsolete. to actuate.

verb phrase

1. act up

   1. to fail to function properly; malfunction.

      The vacuum cleaner is acting up again.

   2. to behave willfully.

      The children always act up in school the day before a holiday.

   3. to become painful or troublesome, especially after a period of improvement or remission.

      My arthritis is acting up again this morning.

2. get / have one's act together to organize one's time, job, resources, etc., so as to function efficiently.

   The new administration is still getting its act together.

3. act on / upon

   1. to act in accordance with; follow.

      He acted on my advice.

   2. to have an effect on; affect.

      The stirring music acted on the emotions of the audience.

4. act out

   1. to demonstrate or illustrate by pantomime or by words and gestures.

      The party guests acted out stories for one another.

   2. Psychology. to give overt expression to (repressed emotions or impulses) without insightful understanding.

      The patients acted out early traumas by getting angry with the analyst.

idioms

1. act one's age, to behave in a manner appropriate to one's maturity.

   We children enjoyed our uncle because he didn't always act his age.

2. clean up one's act, to begin adhering to more acceptable practices, rules of behavior, etc..

   The factory must clean up its act and treat its employees better.

3. act funny, to display eccentric or suspicious behavior.

ACT ² American  

1. Trademark. a standardized college admissions test developed by ACT, Inc., measuring English, mathematics, reading, and science skills: originally an abbreviation of American College Testing/American College Test.

2. Association of Classroom Teachers.

3. Australian Capital Territory.

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act. ³ American  

abbreviation

1. acting.

2. active.

3. actor.

4. actual.

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act ¹ British  

/ ækt /

noun

1. something done or performed; a deed

2. the performance of some physical or mental process; action

3. (capital when part of a name) the formally codified result of deliberation by a legislative body; a law, edict, decree, statute, etc

4. (often plural) a formal written record of transactions, proceedings, etc, as of a society, committee, or legislative body

5. a major division of a dramatic work

6. 1. a short performance of skill, a comic sketch, dance, etc, esp one that is part of a programme of light entertainment

   2. those giving such a performance

7. an assumed attitude or pose, esp one intended to impress

8. philosophy an occurrence effected by the volition of a human agent, usually opposed at least as regards its explanation to one which is causally determined Compare event

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verb

1. (intr) to do something; carry out an action

2. (intr) to function in a specified way; operate; react

   his mind acted quickly

3. to perform (a part or role) in a play, etc

4. (tr) to present (a play, etc) on stage

5. (intr; usually foll by for or as) to be a substitute (for); function in place (of)

6. to serve the function or purpose (of)

   the glass acted as protection

7. (intr) to conduct oneself or behave (as if one were)

   she usually acts like a lady

8. (intr) to behave in an unnatural or affected way

9. (copula) to pose as; play the part of

   to act the fool

10. (copula) to behave in a manner appropriate to (esp in the phrase act one's age )

11. not_standard (copula) to seem or pretend to be

    to act tired

12. to start to behave in a responsible manner

13. informal to become involved in a profitable undertaking or advantageous situation in order to share in the benefits

14. informal to become organized or prepared

ACT ² British  

abbreviation

1. Australian Capital Territory

2. (formerly in Britain) advance corporation tax

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ACT ³ British  

/ ækt /

acronym

1. (in New Zealand) Association of Consumers and Taxpayers: a small political party of the right

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act More Idioms  

More idioms and phrases containing act

• catch in the act
• clean up (one's act)
• do a disappearing act
• get in the act
• get one's act together
• hard (tough) act to follow
• high-wire act
• in the act of
• put on an act

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Synonym Usage

See action.

Other Word Forms

Derived Forms

• actability
  noun
• postact
  noun
• preact
  verb (used with object)
• misact
  verb (used without object)
• actable
  adjective
• unacted
  adjective
• well-acted
  adjective

Inflected Forms

Nouns

• acts
  plural

Participles

• acting
  present
• acted
  past

Conjugated Forms

Present

• act
  simple
• acts
  simple
• have acted
  perfect
• has acted
  perfect
• am acting
  progressive
• are acting
  progressive
• is acting
  progressive
• have been acting
  perfect progressive
• has been acting
  perfect progressive

Past

• acted
  simple
• had acted
  perfect
• was acting
  progressive
• were acting
  progressive
• had been acting
  perfect progressive

Future

• will act
  simple
• will have acted
  perfect
• will be acting
  progressive
• will have been acting
  perfect progressive

Etymology

Origin of act

First recorded in 1350–1400; Middle English act(e), from Middle French, from Latin ācta, plural of āctum “something done,” noun use of neuter past participle of agere “to do, drive”; also from Latin āctus “deed,” noun use of masculine past participle of agere

Explanation

When you do something, you act. A commercial that says "Act now!" means "Get up from the couch and order me! This minute!" Act is both a noun and a verb. You can perform an act of kindness or violence. Or, you can act in a play. People who take on roles and perform them are actors. Likewise, plays, operas, and ballets are broken down into acts. You may have seen references to Shakespeare's plays, such as "Act I, Scene IV." Comedians refer to their shows as acts. Other performers, from magicians to lion tamers, sometimes do the same: a magic act is a magician's show.

Example Sentences

See Examples For:

act ACT act. acts acted acting

The androids, or synthezoids, here are presented for the most part in human form, which is easier on the eyes, the budget and the actors, and gives them room to act.

From Los Angeles Times ● Oct. 14, 2026

Rouhi Fattouh, president of the Palestinian National Council, described the arson attack on the mosque as "a barbaric act and a dangerous escalation in settler terrorism".

From Barron's ● Oct. 14, 2026

“Inflation remains above our goal,” she said Wednesday, but added that she doesn’t feel a sense of urgency to act in the wake of the last rate hike.

From The Wall Street Journal ● Oct. 14, 2026

Arthur said the act was "vital" to driving research needed into the condition, but that Goodburn's meeting with Burnham could lead to further work in the field.

From BBC ● Oct. 14, 2026

Anyway, you can see how Buddy got to be known as the worst boy in Sassafras Springs, even though no one ever caught him in the act, not once.

From "The Seven Wonders of Sassafras Springs" by Betty G. Birney

National Science Foundation through awards AST-0408698, AST-0965625, and AST-1440226 for the ACT project, as well as PHY-0355328, PHY-0855887, and PHY-1214379.

From Science Daily ● Aug. 25, 2026

It's unclear whether the bill will pass, as both National Party's coalition partners -- the libertarian ACT party and NZ First -- have said they oppose it.

From Barron's ● Aug. 24, 2026

Michigan no longer mandates the SAT or ACT for undergraduate admissions.

From The Wall Street Journal ● Aug. 11, 2026

Most speakers were science, technology, engineering and math, or STEM, professors who urged the board to bring back the SAT and ACT.

From Los Angeles Times ● Jul. 14, 2026

Although he had little trouble getting As in classes he liked, he had a C+ average and his ACT test scores were below the mean at the university.

From "Geeks: How Two Lost Boys Rode the Internet Out of Idaho" by Jon Katz

"It's a time to act. It's a time for boldness."

From Barron's ● Oct. 6, 2026

“We know who they are and how they act. So we will be prepared.”

From The Wall Street Journal ● May 28, 2026

But during her sentencing ruling Olivier said "it wasn't... an impulsive act. It was the event of the evening," the AFP news agency reports.

From BBC ● Apr. 16, 2026

“The pause highlights a balancing act. Officials have moved away from peak restriction,” analysts at U.S.

From MarketWatch ● Mar. 31, 2026

"If he did, it was all probably just part of his act. You know, to make people think he's in love with me."

From "The Hunger Games" by Suzanne Collins

The cuts will be automatic unless Congress acts to strengthen the system.

From MarketWatch ● Oct. 12, 2026

Curo said the extra money was primarily to increase the block's sinking fund, which acts as a long-term savings account for building costs.

From BBC ● Oct. 8, 2026

Once inside the joint, the gel acts as a storage site for lacosamide, keeping the medication concentrated in the affected area while gradually releasing it over several weeks.

From Science Daily ● Oct. 8, 2026

But some users find that much like the models they’re built on—which can hallucinate, misinterpret or even commit spontaneous acts of cybercrime—their assistants, too, can behave unpredictably.

From The Wall Street Journal ● Oct. 8, 2026

Zero and infinity made the simple acts of taking tangents and finding areas appear to be self-contradictory.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

It acted as a sort of CarPlay for the home, with an iPhone-like experience tailored to life inside and shared among multiple people.

From The Wall Street Journal ● Oct. 13, 2026

The suspects appear to have acted without a buyer or sponsor, said Antonetti.

From Barron's ● Oct. 12, 2026

Kelker-Kelly primarily acted in TV and was best known for his work in long-running daytime dramas, which also included “Another World.”

From Los Angeles Times ● Oct. 6, 2026

He said Albadri had acted in an "absurd, performative fashion" which was "deliberately designed to draw attention to himself".

From BBC ● Oct. 5, 2026

They acted and felt like the managers of their own fund.

From "The Big Short" by Michael Lewis

A recent sharp rise in government bond yields is acting as a brake on the economy, Moulin noted.

From The Wall Street Journal ● Oct. 14, 2026

My parents divorced, and Mom took acting and modeling jobs.

From The Wall Street Journal ● Oct. 13, 2026

In 2022, Carrey revealed that he was “fairly serious” about stepping away from acting, explaining that he had become content with the life he had created outside the relentless pace of Hollywood.

From MarketWatch ● Oct. 13, 2026

In August 2025, Serhii K was arrested after checking into a hotel near the Italian Adriatic resort of Rimini, by police acting under a European arrest warrant issued by federal prosecutors in Germany.

From BBC ● Oct. 13, 2026

“I am lucky to have her help, but acting isn’t what I’m interested in. It’s the set design that intrigues me.”

From "The Red Car to Hollywood" by Jennie Liu

Related Words

• begin
• carry out
• develop
• do
• enforce
• execute
• function
• move
• operate
• pursue
• respond
• serve
• undertake