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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

By this act, Congress and the president agreed to shift executive-branch functions to the independent GAO, which reported to Congress.

From The Wall Street Journal ● Aug. 11, 2026

The act grants coastal states the right to review and object to any project in federal waters that clashes with state policy.

From Los Angeles Times ● Aug. 11, 2026

The funds focus on lower-risk infrastructure businesses, which act as a tidy diversifier between bonds and equities, portfolio manager Bertrand Cliquet told MarketWatch in an interview on Monday.

From MarketWatch ● Aug. 11, 2026

Joe Root returns as full-time captain on his home ground of Headingley, while Marcus Trescothick will act as interim head coach before Stephen Fleming takes charge for the winter tour of South Africa.

From BBC ● Aug. 10, 2026

“Other kids read the same drivel and they don’t act this way.”

From "The Way to Rio Luna" by Zoraida Cordova

Six years after dropping the SAT and ACT, the University of California is weighing a return to standardized testing following intense pressure from faculty who say incoming students lack basic math and reasoning skills.

From Los Angeles Times ● Jul. 14, 2026

There are early signs that views may have changed in the six years since the governing board unanimously voted to eliminate SAT and ACT requirements.

From Los Angeles Times ● Jul. 9, 2026

Many competitive colleges that dropped the SAT or ACT have restored it because too many incoming students can’t do basic arithmetic or read any but the simplest texts.

From The Wall Street Journal ● Jun. 19, 2026

McClure, from the ACT party, said the travel ban was "a type of foreign interference" and that she was "not going to apologise for visiting Taiwan", the New Zealand Herald reported.

From BBC ● Jun. 4, 2026

The next day, I drove forty miles to the nearest bookstore and bought a glossy ACT study guide.

From "Educated" by Tara Westover

"We have the licensing act. It was created quite a long time ago and it hasn't kept up with the reality on the ground," he says.

From BBC ● May 10, 2026

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

From MarketWatch ● Mar. 31, 2026

"Eastern Africa is on the front line of change, but there is still time to act. Smarter land management -- like conserving forests and restoring vegetation -- can protect rainfall and sustain agricultural growth."

From Science Daily ● Dec. 12, 2025

“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

“Well, partially. It is an act. I am an act. Totally full of it. About ninety-eight percent of the time anyway. My intentions are rarely honorable. It’s not terrible to be called out for once.”

From "I'll Give You the Sun" by Jandy Nelson

At around 8 p.m., night shift workers shut down every gallery in South Hall, locking every prisoner inside his cell, including the porter, who sometimes acts as an additional set of eyes and ears.

From Slate ● Aug. 11, 2026

He added that he did not believe the offences were "spontaneous or accidental acts".

From BBC ● Aug. 10, 2026

It remains the only time that atomic weapons have been used in warfare, and was one of the last major acts of World War II.

From Barron's ● Aug. 9, 2026

Beijing acts on that insight by investing in Arm China and heavily backing RISC-V, an ISA developed at the University of California, Berkeley, in 2010.

From The Wall Street Journal ● Aug. 9, 2026

Alex acts as if it’s my fault everyone talked about me so much.

From "The Manifestor Prophecy" by Angie Thomas

The opticians' manager Fouad Mehdaoui told AFP he acted on a tip from his pharmacist wife, placing large orders of glasses early on, but even then was outrun by demand and had to order more.

From Barron's ● Aug. 11, 2026

It fell apart within a week, predictably, as the two sides acted on conflicting interpretations of its central provisions.

From Slate ● Aug. 10, 2026

He said the new findings provide unusually strong evidence that natural selection acted on this gene in the Andes after potato cultivation began.

From Science Daily ● Aug. 10, 2026

Al-Marimi is said to have told the officer he acted alongside fellow members of the Libyan intelligence service, under the orders of senior officials.

From BBC ● Aug. 7, 2026

“I should have acted sooner. You are safe now, I promise.”

From "The Wild Robot Escapes" by Peter Brown

She has served as acting governor since departure.

From The Wall Street Journal ● Aug. 10, 2026

It doesn’t feel as vulnerable, whereas acting, there’s something fundamentally so indulgent about it.”

From Los Angeles Times ● Aug. 10, 2026

Indonesian President Prabowo Subianto has nominated acting Bank Indonesia Gov. Destry Damayanti as the sole candidate to lead the central bank.

From The Wall Street Journal ● Aug. 10, 2026

The vote brings to an end a lengthy standoff between Senate Republicans and the Trump administration over Blanche, who has served as acting attorney general since April.

From BBC ● Aug. 8, 2026

I walked past the soldiers in my usual way, acting as if I had every right to be on these streets.

From "Code Name Kingfisher" by Liz Kessler

Related Words

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