“I could barely keep a straight face.”

Your daughter made a big mistake on her science homework. It was a really funny mistake but you didn't want to make her feel bad by laughing at her, so you tried to control yourself. Later, you tell your husband about it. You say:

I could barely keep a straight face.

I could barely (do something)

If you "barely" do something, it means that you are able to do it but you almost were not able to. You almost fail. In the example above, the speaker didn't laugh at her daughter but she almost laughed at her.

Here's another example: if you have to return a rental car by 6:00pm but you didn't bring it back until 5:50, you can say:

I just barely made it back in time to return the car.

Say that you "could barely ___" for continuous actions and situations that you had trouble with in the past:

When I first moved to Mexico, I could barely speak Spanish.

keep a straight face

To "keep a straight face" means to avoid laughing. You try to "keep a straight face" when something is funny but you're not supposed to laugh. This happens in situations like:

• when you're in a serious meeting but someone makes a mistake.
• when you're trying to play a trick on someone.
• when you're scolding a child who's been bad but they say something funny.