5. contract

(1) vt. 染上疾病；负上债
My son contracted a severe fever.
He contracted huge debts by rash spending.

(2) vi. 订合同
The factory contracted with a company for 2000 tons of cement.
They contracted to build the new bridge.

(3) vi.&vt. 缩小；缩紧
Metals contract in cold weather.
In conversational English "I will" often contracts to "I'll".

(4) n. 契约；合同
The labor contract has been renewed.
The firm has made a contract with its employees.

6. infect vt.

(1) affect with germ, virus, or disease 传染；染上细菌
Anyone with a bad cold may infect the people around him.
The disease infected her eyes and she became blind.

(2) imbue or taint 感染；影响
The captain's courage infected his men.
One bad boy may infect the whole class.

infection n.
(1) 传染
You can guard against infection by wearing a mask over your face.
Diseases are usually spread by infection.

(2) 传染病
Measles is an infection.

7. act

(1) vi. 采取行动
You will see how I will act.
He was persuaded to act immediately.

(2) vt.&vi. 演出；扮演
I just want to see her act.
He acts very well.
He will act Hamlet tonight.
Acting only one part in this play is enough for her.

(3) vi. 起作用
The brake isn't acting, I am afraid there will be an accident.
act on (upon) 对……起作用
Alcohol acts on the brain.
There are four forces acting on an aircraft as it flies through the air.

(4) n. 行为；行动
That's one true act of friendship.
His first act is to jump off the train.
It's my own act. Why do you bring my mother in?

(5) n. 戏的一幕
It is a play in five acts.
Did you ever try your hand in a one-act play?

(6) n. 法案
the Lend -Lease Act
The Natural Gas Policy Act was passed.