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
acted; acting; acts
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
1
a
: to represent or perform by action especially on the stage
will act the part of Romeo in tonight's play
c
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.
1
active
2
actor
3
actual
1
Action for Children's Television
2
Association of Classroom Teachers
3
Australian Capital Territory
—used for a standardized achievement test to evaluate suitability for college admission
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
Emlyn Travis, Entertainment Weekly, 29 Oct. 2025
For its next act, Only Murders in the Building is returning to its roots.
—Josh Wigler, HollywoodReporter, 28 Oct. 2025
Mike Barnes, HollywoodReporter, 29 Oct. 2025
Toscano argued that Parker had the authority as the assistant principal to act.
—Sarah Rumpf-Whitten, FOXNews.com, 29 Oct. 2025
See All Example Sentences for act
Examples are automatically compiled from online sources to
show current usage.
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Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Noun
There are also several large time skips as the play picks up speed and focuses less on the group in favor of exploring Lizzie’s mother and their family in its second act.
—Emlyn Travis, Entertainment Weekly, 29 Oct. 2025
For its next act, Only Murders in the Building is returning to its roots.
—Josh Wigler, HollywoodReporter, 28 Oct. 2025
Verb
DePriest won a full drama scholarship to the University of Oklahoma and after college acted on stages in Dallas and hosted two local TV shows, Ladies First and Maggie and Her Friends, a kids program with puppets.
—Mike Barnes, HollywoodReporter, 29 Oct. 2025
Toscano argued that Parker had the authority as the assistant principal to act.
—Sarah Rumpf-Whitten, FOXNews.com, 29 Oct. 2025
See All Example Sentences for act
Cite this Entry
“Act.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/act. Accessed 31 Oct. 2025.
Copy CitationKids Definition
act
1 of 2 noun1
: 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 verb1
: 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
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
Legal Definition
act
1 of 2 noun1
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
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 verb1
: 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
U.S. Constitution art. II3
: 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
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