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Sentence Patterns using "I can't understand why..."

This expression is used when the speaker is surprised, confused, annoyed, or angry about something or someone. We can usually tell how the speaker feels by how they say this sentence.

When people are different than us, sometimes they do things that we do not understand. Sometimes, we are surprised or confused when we see these things. But other times, we might be angry or annoyed. We can use this sentence pattern in these situations.
  • I can't understand why you like this song. (Surprise/Confusion/Curiosity)
  • I can't understand why somebody stole my old bike! (Anger)
Subject + can't understand why + sentence
  • I can't understand why women like flowers.
  • I can't understand why you like running. I hate it.
  • I cannot understand why he doesn't like me.
  • I can't understand why you didn't tell me the truth.
  • He can't understand why people throw their trash away on the street.
  • Bob can't understand why people smoke.
  • My wife cannot understand why I like to fall asleep while watching TV.
  • The man can't understand why his son loves dancing so much.
  • The management can't understand why the workers are so angry.
  • The conservatives can't understand why the liberals don't support the tax cut.
We make this sentence past tense by changing the word "cannot" to "could not". This is used to talk about our past feelings.
  • I couldn't understand why she didn't want to take the job at our company, but now I understand.
  • She couldn't understand why I didn't want to go to the beach last week.
  • He couldn't understand why his students didn't understand his explanation.
It is also very common to make sentences with "how" instead of "why".

Subject + can't understand how + sentence
  • I can't understand how you can eat pizza every day.
    (=How can you eat pizza every day?)

  • I can't understand how he made so much money.
  • He cannot understand how I am always happy.
Bonus Tips and Points

1. It is also common to use the same sentence pattern with "what" instead of "why" or "how".
  • I can't understand what he said.
  • I can't understand what he was trying to do when he agreed to this contract.
  • She can't understand what to do.
  • They can't understand what the problem is.
  • You cannot understand what I had to do to get the promotion.
2. We can also make questions.
  • Can you understand why people smoke?
  • Can you understand why I have to quit my job?
  • Do you think he can understand why they refused his offer?
  • Do you think our boss will understand why we are late today?
  • Can you understand why I don't want to take the job?
Real-World English Conversations

A) Disgusting! That man just spit on the street.
B) I hate that! I can't understand why people do that.

A) I can't understand why you like yoga.
B) It is so relaxing and healthy. You should try it.

A) My coworkers can't understand why I don't agree with their idea.
B) Then, you need to sit down and talk to them.

A) Let's eat pizza.
B) I can't understand why you like pizza so much.

A) I slept for 12 hours yesterday.
B) I can't understand how you can sleep for so long.

A) I can't understand why some people talk so loudly on the bus.
B) I know. It is so annoying.
A) It drives me crazy.

A) I need some more hot sauce.
B) I will never be able to understand how you can eat food that is so spicy.
A) I can't understand why you hate spicy food. I'm not strange. You are strange.

Study these free English lessons to improve your English speaking. If you learn these common sentence patterns well, then your English speaking will improve greatly and you will be able to have fluent conversations in English in the near future! Study the lessons well, practice using them at home and in real life, and make sure to come back to review the material so you do not forget.

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