There are 2 definitions of act in English:

act1

Syllabification: act

verb

[no object]
1Take action; do something: they urged Washington to act [with infinitive]: governments must act to reduce pollution
More example sentences
  • This body must act now to urge our fellow legislators in the United States Senate to alleviate this crisis.
  • In the wake of Silent Spring all industrialised societies acted to reduce pollution.
  • We must act before we are punished for moving too slowly.
Synonyms
take action, take steps, take measures, move, react
1.1 (act on) Take action according to or in the light of: I shall certainly act on his suggestion
More example sentences
  • Last but not least, the new Mayor said that he would also be acting on a suggestion by Cllr. Browning.
  • We really do welcome your suggestions and try to act on them when possible.
  • This was because his role in that came to light too late for the Hutton inquiry to act on it.
Synonyms
follow, act in accordance with, obey, heed, comply with; fulfill, meet, discharge
1.2 (act for) Take action in order to bring about: one’s ability to act for community change
More example sentences
  • His espousal of State action, representing the best collective nature of the whole community, was to act for the benefit of all.
  • Napoleon recognized his abilities, promoting him to positions where he could act for the benefit of French science and education.
  • I have more faith in the ability of the general public to act for the greater good in the face of a crisis.
1.3 (act for/on behalf of) Represent (someone) on a contractual, legal, or paid basis: he chose an attorney to act for him
More example sentences
  • According to the new regulations, a representative who acts on behalf of visa-seekers must be authorised and could be an immigration consultant with good standing in the Canadian Society of Immigration Consultants.
  • It is about time the party stopped its pretence of acting on behalf of all the people when the only people it represents are the well off, big business and the privileged.
  • The first stages of a High Court hearing will be heard later this month involving a Dublin law firm acting on behalf of up to 12 individual clients.
Synonyms
represent, act on behalf of; stand in for, fill in for, deputize for, take the place of
1.4 (act from/out of) Be motivated by: you acted from greed
More example sentences
  • That said at the bottom of everything, unless the truth is told, people, no matter how well motivated, have no motivation to act from.
  • There's a difference between thinking someone's strategies are wrong, and thinking them a knave who acts from ignorance at best, and more likely acts from malice.
  • Whether you agree or disagree with his policies, you cannot doubt that he acts from deep convictions, and that he is prepared to take courageous decisions that fly in the face of public opinion.
2 [with adverbial] Behave in the way specified: they followed the man who was seen acting suspiciously he acts as if he owned the place
More example sentences
  • It seems to me like women have to grin and bear a lot, and still feel pressure to act like saintly selfless birth goddesses.
  • Their main function is to act like an annoying salesperson who wouldn't take no for an answer.
  • In order to acclimate him to the wild, Dolittle must teach him the ways of nature and how to act like a real bear.
Synonyms
2.1 (act as/like) Behave in the manner of: try to act like civilized adults
3 (act as) Fulfill the function or serve the purpose of: they need volunteers to act as foster parents
More example sentences
  • Police believe their presence also acts as a deterrent against other crimes.
  • Jody acts as a foster mum and he had to hand feed the four every three hours for the first four days.
  • The forum is also looking for volunteers to act as rangers along the trail.
Synonyms
operate, work, function, serve
3.1Have the effect of: a five-year sentence will act as a deterrent
More example sentences
  • All anticonvulsants act through their effect on the brain, since seizures arise from the brain.
  • Ritalin acts on the nicotinic receptors that smokers have long exploited.
  • Although not a benzodiazepine (like Valium, for example), it acts on the same parts of the brain.
4Take effect; have a particular effect: bacteria act on proteins and sugar
More example sentences
  • Thus, the competition between monovalent and divalent cations acts only on the DNA sites and does not act on the mica sites.
  • Drug use was pandemic at these shows because drugs act to trigger the transformation into the private self.
  • The scientists further found that the crumpled ball displayed a phenomenon known as hysteresis, in which the effect of forces acting upon an object lags behind its cause.
Synonyms
affect, have an effect on, work on; have an impact on, impact on, influence
5Perform a fictional role in a play, movie, or television production: she acted in her first professional role at the age of six
More example sentences
  • He is still afraid of accepting film roles, despite having acted in more than 300 films over the past 29 years.
  • He has also acted in a prominent role in a Telugu film.
  • Boorman, son of the director John Boorman, had acted in 24 films since a childhood role in Deliverance in 1972.
Synonyms
perform, play a part, play-act, take part, appear
informal tread the boards, ham it up
5.1 [with object] Perform (a part or role): he acted the role of the dragon he got the chance to act out other people’s jobs
More example sentences
  • In the movie the song is sung with much beauty and accurate feeling by Frank Patterson, the great Irish tenor who also acts the role of Bartell D' Arcy.
  • The player acts the role of a street thug with 40 different weapons.
  • He acts the role of a coward in the face of his own life's work.
5.2 [with complement] Behave so as to appear to be; pretend to be: I acted dumb at first
More example sentences
  • She'd planned to act dumb and pretend she'd never known he was there.
  • So the suspicion remains that his main desire is merely to appear to be acting tough - whether or not what he suggests will make any difference.
  • He acted shocked then pretended to weep.
Synonyms
pretend, play-act, put it on, fake it, feign it, dissemble, dissimulate
5.3 [with object] (act something out) Perform a narrative as if it were a play: encouraging students to act out the stories
More example sentences
  • The premise: during the tail end of a sleep-over, a half-dozen of his child-centered stories are acted out by a quartet of overly wound-up kids stubbornly avoiding sleep.
  • He proceeds to dazzle them with a story, acting it out with the help of his dog.
  • We played outside, made up stories, acted them out, etc.
5.4 [with object] (act something out) Psychoanalysis Express repressed or unconscious feelings in overt behavior: the impulses of hatred and killing which some human beings act out
More example sentences
  • According to Freud, ‘we may say that the patient does not remember anything of what he has forgotten and repressed, but acts it out.’
  • If we can stay with it, neither acting it out nor repressing it, it wakes us up.
  • Like so many traumatized children, they were acting it out again and again, Elliott explains, until they could see it in a way that made sense to them.

noun

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1A thing done; a deed: a criminal act the act of writing down one’s thoughts an act of heroism
More example sentences
  • The bombings were the act of criminal extremists.
  • Witnesses to the act of criminal genius called police who, so far, have only charged the man with theft.
  • Transgression of this boundary was the act of a criminal and a heroic nature.
Synonyms
deed, action, feat, exploit, move, gesture, performance, undertaking, stunt, operation; achievement, accomplishment
2 [in singular] A pretense: she was putting on an act and laughing a lot
More example sentences
  • Kazza stared at me blankly in reply, knowing I was putting on an act.
  • It would be like putting on an act to get others to advance toward God, when I'm still getting a toe on the starting line.
  • It is hoped, for the sake of millions of poor Filipinos, that he is not just putting on an act, good movie actor that he was.
Synonyms
pretense, show, front, facade, masquerade, charade, posture, pose, affectation, sham, fake
informal put-on
2.1 [with adjective or noun modifier] A particular type of behavior or routine: he did his Sir Galahad act
More example sentences
  • In the end, I decided to join in with everyone else and dance - it's hard to keep up the sulky act ALL night.
  • The kitchen where Willie did his Jamie Oliver act makes the one he'll have to share at college look in need of a visit from environmental health.
  • I've brought home a stack of proofs to read this weekend, so started on them on the train home, but did my worryingly regular falling asleep act not long outside London.
3 Law A written ordinance of Congress, or another legislative body; a statute: the act to abolish slavery
More example sentences
  • First established in 1789 by an Act of Congress, the United States Department of the Treasury is responsible for federal finances.
  • It had passed an Act of Parliament to end the proceedings and preclude any appeal.
  • Some of these rights and liberties are the results of custom and convention, whereas others are contained in the written Acts of Parliament.
Synonyms
law, decree, statute, bill, act of Congress, enactment, resolution, edict, dictum, ruling, measure; ordinance
3.1A document attesting a legal transaction.
More example sentences
  • A notary draws up the act which is the legal evidence of the pope's death.
  • Third, the fact that the act or document is uncommercial, or even artificial, does not mean that it is a sham.
  • In my judgment, the law does not require that in every situation every party to the act or document should be a party to the sham.
3.2 (often acts) dated The recorded decisions or proceedings of a committee or an academic body.
More example sentences
  • For the Acts and Proceedings of the Convocations, readers are referred to The Chronicle of the Convocation of Canterbury.
4A main division of a play, ballet, or opera.
More example sentences
  • The play's careful and logical division into five acts (which would have been marked by Intervals in indoor performance) would support this view.
  • With a top ticket price of $110, you had better give me more than a one-act ballet stretched into two acts.
  • Giselle a ballet in two acts begins at 7.30 pm on Friday, April 1, at The Sands Centre, Carlisle.
Synonyms
division, section, subsection, part, segment
4.1A set performance: her one-woman poetry act
More example sentences
  • The performances included 5 separate acts by Madame Jim, with full costume changes, which earned mountains of applause.
  • The comic had risen through the standup ranks, working hard at developing an act after his initial performances drew derision.
  • After I'd done my comedy act during the late seventies, I started writing a screenplay for a movie.
Synonyms
performance, routine, number, sketch, skit, shtick, turn
4.2A performing group: an act called the Apple Blossom Sisters
More example sentences
  • There will be over thirty DJs and live dance acts performing on the day.
  • Both acts performed on the Sunday of the event, Razorlight entertaining on the main stage whilst Babyshambles took to the NME / Radio 1 Stage.
  • Bringing pop acts to perform with an orchestra is a good idea, but too often the symphony takes a back seat to the star.

Origin

late Middle English: from Latin actus 'event, thing done', act- 'done', from the verb agere, reinforced by the French noun acte.

Phrases

act of God

An instance of uncontrollable natural forces in operation (often used in insurance claims).
More example sentences
  • Storms and other natural disasters are just those: natural disasters and not acts of God.
  • Both sides should just batten down the hatches, prepare for a very long 2004 and remember that miracles, or even acts of God, do happen.
  • Natural calamities are always a tragedy and an act of God.

act of grace

A privilege or concession that cannot be claimed as a right.
More example sentences
  • A pardon is an act of grace, proceeding from the power entrusted with the execution of the laws which exempts the individual, on whom it is bestowed, from the punishment the law inflicts for a crime he has committed.
  • A presidential pardon is an act of grace or mercy, proceeding from the power entrusted with the execution of laws, which exempts the individual, on whom it is bestowed, from punishment the courts inflict for a crime he or she committed.
  • Furthermore, under articles 296 and 297 of the Versailles Treaty all enemy aliens lost their beneficial interests in property held in Britain as of 11 January 1920; some exceptions were made as an act of grace but not as a legal right.

catch someone in the act

(usually be caught in the act) Surprise someone in the process of doing something wrong: the thieves were caught in the act
More example sentences
  • I followed her gaze to see Carter, who looked like he had been caught in the act of doing something wrong.
  • They return the next night after Jule realises she has left her mobile somewhere in the house, but Hardenberg surprises them and catches them in the act.
  • A German company has sacked one of its employees for smoking at home after hiring a detective to catch him in the act.

clean up one's act

Behave in a more acceptable manner.
More example sentences
  • After his release from prison, he took steps to clean up his act and get involved in the community.
  • That's why it is so important for all of us to clean up our act and learn how to prevent such pollution.
  • Today the Commons has a choice - to clean up our act or to acquiesce with bigotry and prejudice.

get one's act together

informal Organize oneself in the manner required in order to achieve something.
More example sentences
  • You need to get a grasp of the evidence, and in effect, get your act together.
  • Farming organisations across Europe must get their act together to demand fairer prices from supermarkets for their members.
  • That is why we need to get our act together in terms of organisation and resources so people get the best possible treatment.

get (or be) in on the act

informal Become or be involved in a particular activity, in order to gain profit or advantage.
More example sentences
  • And libraries have also been getting in on the act with book quizzes and other activities to help youngsters experience the magic of reading.
  • One member said: ‘He has not got involved at all with this and just wants to get in on the act for publicity purposes to make it look as though he has helped resolve it.’
  • He saw that direct banking was the future and he thought it essential that the company was in on the act.

in the act of

In the process of: they photographed him in the act of reading other people’s mail
More example sentences
  • His wife smelt something burning and went to investigate, only to find him in the act of now setting the room on fire.
  • Police believe he was in the act of transporting the bomb for paramilitary use when it blew up.
  • Why should they benefit from the protection of individual rights when they are in the act of violating another's rights?

read someone the Riot Act

a tough (or hard) act to follow

An achievement or performance that sets a standard regarded as being difficult for others to measure up to.
More example sentences
  • Stephenson can be justifiably proud of his achievements over the last three seasons and John has a hard act to follow.
  • He gave a huge investment of his time and was a tough act to follow.
  • And I'm thinking, Broadway, ‘Producers,’ that's a tough act to follow.

Phrasal verbs

act out

Misbehave, especially when unhappy or stressed: many children who act out while awaiting placement in a health care facility end up in juvenile detention
More example sentences
  • If it thinks it is the dominant dog, it will also be stressed, and act out very negatively.
  • They need to know how to manage someone who is frustrated, who may not be able to communicate, and who will act out if they are unhappy.
  • He acts out aggressively as a response to being territorial (wanting to be the only one on a slide - or possessive - wanting a toy train all to himself).

act up

(Of a thing) fail to function properly: the plane’s engine was acting up
More example sentences
  • The laptop computer that we have been using for performing pulmonary function tests had been acting up lately, overheating and shutting itself off.
  • Then again, my body did like to pick the wrong times to start acting up.
  • I think the service is messed up here, it was acting up before the phone broke.
Synonyms
malfunction, go wrong, be defective, be faulty
informal be on the blink, be on the fritz
(Of a person) misbehave.
Synonyms
misbehave, behave badly, be up to mischief, become unruly

Derivatives

actability

Pronunciation: /ˌaktəˈbilitē/
noun
sense 5 of the verb.
More example sentences
  • Granville-Barker's ‘Preface’, of 1927, successfully refutes Lamb's criticism of the play's actability.
  • A way to endorse social actability by allowing artists, DJ's and audience to participate in live battles.
  • Filmwriting for actability, action, and structure.

actable

adjective
sense 5 of the verb.
More example sentences
  • By 1825, when his translations of altogether ten plays had been augmented by P. F. Wulff, Denmark and Norway had a partial Shakespeare, heavily weighted towards tragedies and histories but both readable and actable.
  • Heaney has not only come up with a superbly actable text; he clearly realises that the play offers a genuinely Hegelian dialectic between the individual and the state.
  • Sophocles writes glorious poetry and poetic prose to which Frank McGuinness's translation does splendid, actable justice.

Definition of act in:

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Word of the day dinkum
Pronunciation: ˈdiNGkəm
adjective
(of an article or person) genuine

There are 2 definitions of act in English:

ACT2

Syllabification: ACT

abbreviation

1 trademark American College Test.
1.1Australian Capital Territory.

Definition of act in: