stuff

"Stuff" can mean almost any physical items or material.

It's similar to the word "things", but "things" are countable and "stuff" is not. So "stuff" is better to use when you're talking about a group of things that are different from each other - different sizes, shapes, etc.

"Stuff" is especially used to refer to things that you buy or own:

There's a good chance that you'll end up buying a lot of stuff while you're there.

I'll go pick up all the stuff we need.

Excuse me. Would you mind watching over my stuff for me for just a minute?

But "stuff" can also mean "topics" or "ideas", like in this example:

We have a lot of stuff to talk about.

don't you think?

Use this question to ask for agreement from a listener. People use this expression when:

• they're making a suggestion:
  

  You should ask the professor for help, don't you think?

• they want to state their opinion, but they don't feel confident enough to just directly say it
• they want the listeners to feel included in the statement
  

  Wow. I love this place. It's great, don't you think?

• they want the listener to admit that something is true:
  

  You're too old for that, don't you think?

(a body part) gets infected

When a part of your body "gets infected", it means that bacteria enters it and causes problems like pain, redness, and strange fluids.

You can also say that a person "gets infected" when they get a virus or other contagious illness.:

Over 3,000 people in New York have been infected with the bird flu.

keep (something) from (doing something)

When you don't want something to happen, you try to "keep it from" happening:

You have to stir it to keep it from getting burnt.

I tried to keep him from leaving, but he was determined to go.

This phrase is used in spoken English. A more formal phrase with a similar meaning is "prevent (something)":

You should apply an antibacterial ointment to the cut to prevent infection.