I don't know how to swim.

Source: Tatoeba

In the 21st century, it will be hard to survive if you don't know how to use a computer or if you don't know any foreign languages.

Source: Tatoeba

I don't know what you mean.

Source: Tatoeba

I don't understand Chinese, but I want to learn.

Source: Tatoeba

Mark the words that you cannot understand.

Source: Tatoeba

You do not understand.

You don't understand.

You're not getting it.

Source: Tatoeba

No, I don't understand.

Source: Tatoeba

I didn't get his joke.

Source: Tatoeba

I don't understand what I'm saying.

Source: Tatoeba

I'm so dumb... I'm trying to explain things to you that I don't understand myself.

I was a fool to have tried explaining something to you that I don't understand myself.

Source: Tatoeba

I don't understand why pepperoni pizza is so popular.

Source: Tatoeba

I don't understand these.

Source: Tatoeba

The boy doesn't know how to behave.

Source: Tatoeba

So you don't understand this sentence?

Source: Tatoeba

I truly do not understand the question.

I really don't understand this problem.

Source: Tatoeba

How can Tom not understand that?

Source: Tatoeba