they

People often use "they" to mean the people who are responsible for something. For example:

They should clean up the sidewalks here.

In this example, you don't know or care who exactly is supposed to do this; you just think that the people or department which takes care of the sidewalks should do it.

"They" can mean:

• the government
• the police
• the people who manage a building
• the people who run large companies

In other cases, when you use the word "they", you have to explain who you're talking about first. Imagine that someone says:

They came to the beach house.

If you didn't know who the speaker was talking about, you would ask:

Who did?

But when "they" means "the people in charge", you don't need to explain who you mean. 

(police) suspect (a crime)

When something bad happens like someone dying or things being stolen, the police try to figure out what happened. Sometimes it's not clear exactly what happened. In this case, the police first guess what kind of crime it is.

For example, if a man died at home alone, there might be a few different explanations. If the police think that the man died from doing drugs, you can say this:

The police suspect a drug overdose.

If they think that someone killed the man, you can talk about it like this:

They suspect murder.

foul play

"Foul play" is a phrase that we use to talk about a crime. Most often, "foul play" means murder:

The official story is that he died of a heart attack, but some folks believe there was foul play involved.

But it's also possible to use it to talk about other crimes, like robbery.

The phrase "foul play" sounds a little mysterious.