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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

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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

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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

“I would want to act more quickly if inflation expectations drift up, if wage pressures build, or if underlying inflation moves higher,” she said.

From The Wall Street Journal ● Nov. 10, 2026

Moreover, the act provides that Congress can force termination of American engagement at any time by concurrent resolution of both houses.

From Slate ● Nov. 10, 2026

He said Brand harboured a "casual arrogant disregard to any woman's right to say no to you", while his fame meant he believed "you could act when you liked and how you liked".

From BBC ● Nov. 9, 2026

Barrot said France had summoned the Iranian ambassador to Paris "to lodge a very strong protest against this extremely grave act".

From Barron's ● Nov. 9, 2026

How did I expect to get away with such a blatant act of vandalism?

From "Split the Sky" by Marie Arnold

Combined with their coalition partners ACT and New Zealand First, they would have a slim lead over the left-leaning bloc if a deal could be reached.

From BBC ● Nov. 7, 2026

In Chicago, ACT UP’s Gregg Bordowitz became her mentor and professor, and for three years, Rosales immersed herself in learning, becoming obsessed with Gertrude Stein and philosophers like Gilles Deleuze.

From Los Angeles Times ● Sep. 9, 2026

To investigate which explanation better fits the evidence, the researchers analyzed ACT observations of the cosmic microwave background, or CMB.

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

After Dad went to bed, Richard told me that he’d taken a practice test for the ACT.

From "Educated" by Tara Westover

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

From Barron's ● Oct. 6, 2026

Prominent human rights activist Gauri Pradhan called the attack a "very painful incident and the government should punish anyone involved in such atrocious act. There should be some serious efforts for wider reforms".

From BBC ● Aug. 24, 2026

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

From MarketWatch ● Mar. 31, 2026

“Charlie and I encountered this problem several times and failed to act. This failure can be a huge mistake.”

From The Wall Street Journal ● Nov. 10, 2025

“I think it was all an act. How could he have done what he did out there after just a few days? I ain’t buyin’ it.”

From "The Maze Runner" by James Dashner

Kim is a former US Attorney for New York's Southern District and spent several years working as a government attorney focused on fraud and other criminal acts.

From BBC ● Nov. 10, 2026

The company acts as a middleman in the global AI trade, connecting companies, led by Nvidia, that develop hardware to the companies that need computing power for AI.

From The Wall Street Journal ● Nov. 9, 2026

During the Mass, Leo described the Christian family as "a pillar" amid the uncertainties of modern life and urged parents to pass on the faith through simple acts such as prayer, forgiveness and mutual listening.

From Barron's ● Nov. 9, 2026

The web infrastructure and security firm inspects online traffic, helps sites load quickly and acts as a tollbooth for AI bots.

From MarketWatch ● Nov. 5, 2026

“Those little daily acts of thoughtfulness were much appreciated and the men soon loved him.”

From "Death on the River of Doubt" by Samantha Seiple

Authorities didn’t name the suspect, but said he is a Polish citizen in his 20s who they believe acted alone.

From The Wall Street Journal ● Nov. 7, 2026

Nunez has said that since the beginning of the high-school protest movement police had acted with "the greatest proportionality".

From Barron's ● Nov. 6, 2026

You have acted unilaterally and spent $25,000 of your savings to bail your sister out of trouble.

From MarketWatch ● Nov. 6, 2026

"But thankfully she acted quickly and rescued the young lad and got him help from the emergency services."

From BBC ● Nov. 3, 2026

He acted like he was jealous of the little mare.

From "Summer of the Monkeys" by Wilson Rawls

Smiths pivoted to acting in the 1980s and her first screen credits included a few episodes of “Miami Vice” in 1987 and the 1988 feature “Me and Him.”

From Los Angeles Times ● Nov. 10, 2026

Its familiar, rapidly acting signals help us respond to opportunities for reward.

From Science Daily ● Nov. 9, 2026

“We see a lot of retirements coming, and the airlines are growing,” said Katie Pribyl, acting co-president of the Aircraft Owners and Pilots Association.

From The Wall Street Journal ● Nov. 7, 2026

The boggy areas of the fire site sustained the least damage, acting as a barrier to help slow the blaze from moving more widely across forest, and have recovered the quickest.

From BBC ● Nov. 7, 2026

“How do you stop the children from acting like wolves?”

From "The Interrupted Tale" by Maryrose Wood

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