charitable, kind
heroic, selfless
a heroic act of bravery

aggressive, barbaric, hostile, provocative, terrorist, violent
He was arrested on suspicion of planning terrorist acts.

appalling (esp. BrE), cowardly, despicable, heinous, horrific, immoral, outrageous, terrible, unspeakable
appalling acts of cruelty
horrific acts of violence

criminal, delinquent (esp. AmE), illegal, unlawful, wrongful
careless (esp. BrE), foolish, impulsive
conscious, deliberate, intentional, positive, voluntary, wilful/willful
The company says that the explosion was no accident but a deliberate act of sabotage.

private, public
a private act of revenge

creative, dramatic, physical, political, symbolic
homosexual, sex, sexual
random
random acts of violence

carry out, commit (law), perform, perpetrate
images of African Americans performing heroic acts
charged with committing an act of gross indecency

condemn
condone, justify
prevent
witness

in the act of (= while doing something)
act of
For Jane, the act of writing was always difficult.

an act of faith, an act of love, an act of violence, an act of will, an act of worship
a hard act to follow, a tough act to follow
Their contribution will prove a hard act to follow.

catch sb in the act (of doing sth)
He was caught in the act of stealing.

the simple act of doing sth, the very act of doing sth
The very act of writing out your plan clarifies what you need to do.

bring in (BrE), introduce, pass
The Act was passed by a majority of 175 votes to 143.

amend
repeal
The old act has now been repealed.

breach (esp. BrE), contravene (BrE), violate (esp. AmE)
The company had violated the Data Security Act of 2006.

become law, come into force (BrE)
The new Children's Act will become law next year.

contain sth, say sth, state sth
The act contains regulations for financial institutions.

apply to sth
The 1995 act applies only to food and not to dietary supplements.

require sth
prohibit sth

under an/the act
He was charged under the Firearms Act.

class (informal) (used for sb who does sth well)
Their new player looks a class act.

solo
double
comedy double act French and Saunders

live
their reputation as one of rock's most impressive live acts

main, support
The main act will come on at about ten o'clock.

opening
cabaret, circus, comedy, dance, drag, music, musical, novelty, stage, stand-up, variety
The club offers live music and cabaret acts.
The group is merely a novelty act (= an act that is only interesting because it is strange or unusual).

hip-hop, pop, rock, etc.
balancing, disappearing, juggling, vanishing (all figurative)
The cat had done a disappearing act.
The UN must perform a difficult balancing act between the two sides in the conflict.

do, perform
He does a little novelty act.

rehearse, work on
I have to work on my act.

opening
final, last
first, second, etc.

in (the) act
The king is killed in the opening act.

put on
Don't take any notice—she's just putting on an act!

at once, immediately, promptly, quickly, swiftly
The government must act promptly to change this law.

appropriately, correctly, legally, properly
dishonestly, illegally, improperly, inappropriately, unconstitutionally, unlawfully, wrongly
The country's highest court ruled that police had acted unlawfully.

rationally, reasonably, responsibly, sensibly (esp. BrE), wisely
All citizens have a duty to act responsibly and show respect to others.

irrationally, irresponsibly, rashly, unreasonably
oddly, strangely, suspiciously
Jenny has been acting rather strangely recently.

bravely, heroically
decisively
The government was criticized for failing to act decisively.

aggressively
independently, unilaterally
effectively
in self-defence/self-defense
The jury accepted that he had acted in self-defence/self-defense.

accordingly
George knew about the letter and acted accordingly.

against
The government needs to act against the sale of these dangerous toys.

for sb, on behalf of sb
His lawyers are continuing to act for him.

like
Stop acting like a spoiled child.
hormones in the brain that act like natural painkillers

on
Alcohol acts quickly on the brain.

out of
I suspected that he was acting out of malice.

act as if
She was acting as if she owned the place.

act in sb's best interests
We are all acting in the best interests of the children.

act in good faith
His excuse was that he had acted in good faith.

brilliantly, well
The play is well acted.

badly, poorly

Act is used with these nouns as the subject:
actor, actress

Act is used with these nouns as the object:
age, part, scene