“This is why” and “This is how”

Great — “This is why” and “This is how” are both commonly used expressions, but they introduce very different kinds of information. Here's a simple and clear breakdown:


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1. This is why...

Use it to explain a reason or cause.

Often follows an event or situation and leads to an explanation.


Examples:

He didn’t study. This is why he failed the exam.

I missed the bus. This is why I was late.


Think: Cause → This is why → Effect


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2. This is how...

Use it to explain a method, process, or manner.

Often shows steps, actions, or the way something happened.


Examples:

She trained every day. This is how she became a great athlete.

This is how you make kimchi: first, prepare the cabbage...


Think: Process or method → This is how → Result


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Side-by-side Example:

I forgot to set my alarm. This is why I overslept. → (reason)

I set two alarms and put my phone across the room. This is how I avoid oversleeping. → (method)