Collins COBUILD Advanced Learner’s Dictionary

1 VERB When you act , you do something for a particular purpose. □ [V ] The deaths occurred when police acted to stop widespread looting and vandalism. □ [V adv/prep] I do not doubt that the bank acted properly.

2 VERB If you act on advice or information, you do what has been advised or suggested. □ [V + on/upon ] A patient will usually listen to the doctor's advice and act on it.

3 VERB If someone acts in a particular way, they behave in that way. □ [V adv] …a gang of youths who were acting suspiciously. □ [V + as if ] He acted as if he hadn't heard any of it. □ [V + like ] Open wounds act like a magnet to flies.

4 VERB If someone or something acts as a particular thing, they have that role or function. □ [V + as ] He acted as the ship's surgeon. [Also V + like ]

5 VERB If someone acts in a particular way, they pretend to be something that they are not. □ [V adj] Chris acted astonished as he examined the note. □ [V n] Kenworthy had tried not to act the policeman.

6 VERB When professionals such as lawyers act for you, or act on your behalf , they are employed by you to deal with a particular matter. □ [V + for ] Lawyers acting for the families of the victims … □ [V prep] Because we travelled so much, Sam and I asked a broker to act on our behalf.

7 VERB If a force or substance acts on someone or something, it has a certain effect on them. □ [V + on/upon ] The drug acts very fast on the central nervous system. [Also V ]

8 VERB If you act , or act a part in a play or film, you have a part in it. □ [V ] She confessed to her parents her desire to act. □ [V + in ] She acted in her first film when she was 13 years old. [Also V n]

9 N‑COUNT An act is a single thing that someone does. [FORMAL ] □ [+ of ] Language interpretation is the whole point of the act of reading.

10 N‑SING If you say that someone's behaviour is an act , you mean that it does not express their real feelings. □  His anger was real. It wasn't an act.

11 N‑COUNT An Act is a law passed by the government. □ [+ of ] …an Act of Parliament.

12 N‑COUNT An act in a play, opera, or ballet is one of the main parts into which it is divided. □  Act II contained one of the funniest scenes I have ever witnessed.

13 N‑COUNT An act in a show is a short performance which is one of several in the show. □  This year numerous bands are playing, as well as comedy acts.

14 PHRASE If you catch someone in the act , you discover them doing something wrong or committing a crime. □ [+ of ] The men were caught in the act of digging up buried explosives.

15 PHRASE If someone who has been behaving badly cleans up their act , they start to behave in a more acceptable or responsible way. [INFORMAL ] □  The nation's advertisers need to clean up their act.

16 PHRASE If you get in on the act , you take part in or take advantage of something that was started by someone else. [INFORMAL ] □  Unsurprisingly, other firms are keen to get in on the act.

17 PHRASE You say that someone was in the act of doing something to indicate what they were doing when they were seen or interrupted. □  Ken was in the act of paying his bill when Neil came up behind him.

18 PHRASE If you get your act together , you organize your life or your affairs so that you are able to achieve what you want or to deal with something effectively. [INFORMAL ] □  The Government should get its act together.

19to act one's age → see age

20to act the fool → see fool