act

1 of 5

noun

ˈakt 

1

a

: the doing of a thing : deed

an act of courage

b

law : something done voluntarily

2

: the process of doing something : action

caught in the act

3

: the formal product of a legislative body : statute

an act of Congress

also : a decision or determination of a sovereign, a legislative council, or a court of justice

4

: one of the principal divisions of a theatrical work (such as a play or opera)

a play in three acts

5

a

: one of successive parts or performances (as in a variety show or circus)

a magic act

b

: the performer or performers in such an act

a two-person comedy act

c

: a performance or presentation identified with a particular individual or group

They took their act on the road.

d

: the sum of a person's actions or effects that serve to create an impression or set an example

a hard act to follow

6

: a display of affected behavior : pretense

put on an act that deceived nobody

His friendly concern was just an act.

7

often capitalized : a formal record of something done or transacted

8

: a state of real existence rather than possibility

act

2 of 5

verb

acted; acting; acts

intransitive verb

1

: to take action : move

think before acting

acted favorably on the recommendation

2

: to conduct oneself : behave

act like a fool

3

a

: to perform on the stage

began acting at the age of eight

b

: to behave as if performing on the stage : pretend

seemed angry but was just acting

4

: to perform a specified function : serve

trees acting as a windbreak

5

: to produce an effect : work

wait for a medicine to act

6

: to give a decision or award

adjourned without acting on the bill

7

of a play : to be capable of being performed

a play that acts well

transitive verb

1

a

: to represent or perform by action especially on the stage

will act the part of Romeo in tonight's play

b

: feign, simulate

act indifference

c

: impersonate

2

: to play the part of as if in a play

act the man of the world

3

: to behave in a manner suitable to

Act your age.

4

obsolete : actuate, animate

actability

ˌak-tə-ˈbi-lə-tē 

noun

actable

ˈak-tə-bəl 

adjective

act

3 of 5

abbreviation (1)

1

active

2

actor

3

actual

ACT

4 of 5

abbreviation (2)

1

Action for Children's Television

2

Association of Classroom Teachers

3

Australian Capital Territory

ACT

5 of 5

trademark

ˌā-ˌsē-ˈtē 

—used for a standardized achievement test to evaluate suitability for college admission

Phrases

into the act or in on the act

: into an undertaking or situation as an active participant

saw the success they were having and wanted to get in on the act

Synonyms

Noun

• bit
• number
• routine
• shtick
• schtick
• shtik
• turn

Verb

• do
• impersonate
• interpret
• perform
• play
• portray

Examples of act in a Sentence

Noun

We were grateful for her many acts of kindness.

the Civil Rights Act of 1964

Please read act II, scene 1 of Shakespeare's Romeo and Juliet.

In the first act, two characters are talking in a restaurant.

Verb

He knew he had to act quickly.

The government was slow to act.

She acted on behalf of her father, who was not at the meeting.

I believe that the killer acted alone.

She had acted in self-defense when she killed her attacker.

We were acting in the best interests of our children.

We must act soon to end this crisis.

She learned at an early age how to act properly in social situations.

People are always telling me how I should act and what I should say.

I noticed that the dog was acting funny this morning.

Recent Examples on the Web

Noun

Grace reminds us that spaceflight is not just a feat of engineering, but an act of goodwill to the benefit of every human everywhere. —ArsTechnica, 27 June 2025

The group relocated briefly to San Francisco in 1966, playing gigs and honing their live act. —Gail Mitchell, Billboard, 27 June 2025

Verb

Even if borrowers act immediately, there simply may not be enough time to enroll in ICR. —Adam S. Minsky, Forbes.com, 28 June 2025

The actress, who broke through with her Oscar-winning performance in the 1990 film Misery, has over 200 acting and directing credits to her name. —Brendan Le, People.com, 28 June 2025

Word History

Etymology

Noun

Middle English acte, borrowed from Anglo-French & Latin; Anglo-French acte, act, borrowed partly from Latin āctus "driving of cattle, track for cattle, movement, activity, performance, part of a play" (action noun from agere "to drive (cattle), cause to move, do"), partly from Latin āctum (usually in plural) "thing done, public transaction, record," from neuter of āctus, past participle of agere — more at agent

Verb

Middle English acten "to act upon, adjudicate," in part derivative of act act entry 1, in part borrowed from Latin āctus, past participle of agere

First Known Use

Noun

14th century, in the meaning defined at sense 1a

Verb

1590, in the meaning defined at intransitive sense 2

Phrases Containing act

• act accordingly
• act dumb
• act of God
• act one's age
• act on/upon
• act out
• act/play the fool
• act the part
• act up
• a hard/tough act to follow
• balancing act
• caught in the act
• class act
• clean up one's act
• co-act
• get in on the act
• get into the act
• get one's act together
• high-wire act
• in the act (of doing something)
• into the act
• juggling act
• pull a vanishing act
• put on an act
• read the riot act
• riot act
• sex act
• the sex act

Rhymes for act

• backed
• blacked
• bract
• cracked
• fact
• hacked
• jacked
• lacked
• packed
• pact
• racked
• sacked

Kids Definition

act

1 of 2 noun

ˈakt 

1

: something that is done

an act of kindness

2

: the doing of something

caught in the act

3

: a law made by a governing body

an act of Congress

4

a

: one of the main divisions of a play or opera

b

: one of the parts of a variety show or circus

5

: a display of behavior that is not sincere

just putting on an act

act

2 of 2 verb

1

: to perform by action especially on the stage

2

: to play the part of

act the man of the world

3

a

: to behave in a manner suitable to

act your age

b

: to conduct oneself

act like a fool

4

: to take action : move

think before you act

5

a

: to perform a function : serve

act as mayor

b

: to produce an effect : work

wait for a medicine to act

Etymology

Noun

Middle English act "act, deed," from Latin actus "action of doing" and from Latin actum "something done," both from agere "to drive, do" — related to agent

Medical Definition

act

1 of 3 noun

ˈakt 

1

: a motor performance leading to a definite result

2

: a dealing with objects (as by moving, perceiving, or desiring them)

act

2 of 3 intransitive verb

1

: to perform an act : behave

2

: to produce an effect

wait for a medicine to act

act

3 of 3 abbreviation

active

Legal Definition

act

1 of 2 noun

1

a

: something done by a person in accordance with his or her free will

a tortious act

see also actus reus

b

: the failure to do something that one has a legal duty to do

called also negative act

2

a

often capitalized : the formal product of a legislative body : the formally declared will of a legislature the final requirement of which is usually the signature of the proper executive officer : statute

an act of Congress

in furtherance of the purposes…of that act

—U.S. Code

b

: a decision or determination of a sovereign, a legislative council, or a court of justice compare bill sense 1

3

often capitalized : a formal record of something done or transacted

given as my free act and deed

act

2 of 2 intransitive verb

1

: to carry into effect a determination of the will : take action

2

: to discharge the duties of a specified office or post : perform a specified function

—used with a prepositional phrase

declaring what officer shall then act as President

—U.S. Constitution art. II

3

: to give a decision or award (as by vote of a deliberative body or by judicial decree)

—often used with on

adjourned with several important matters still not acted on

actor

ˈak-tər 

noun