That's why

USAGE SUMMARY

"that's why" is correct and can be used in written English.
It is used to explain the reason for something. For example: I don't have enough money to go on the trip, that's why I can't come with you.

✓ Grammatically correct

News & Media

Science

Human-verified examples from authoritative sources

Exact Expressions

60 human-written examples

"That's why it's disappointing".

The New York Times

That's why they're politics.

The New Yorker

That's why I watch.

The New York Times

That's why elections matter.

The New York Times

That's why galleries cluster.

The New York Times

That's why I'm disappointed.

Independent

That's why it's red".

The New Yorker

"That's why this happens".

The New York Times

That's why I'm running".

The New York Times

That's why they're great".

The New Yorker

That's why I did".

Independent

Expert writing Tips

Best practice

Use "That's why" to clearly and directly explain the cause or reason behind a statement. This phrase is suitable for both informal and moderately formal contexts.

Common error

In highly formal or academic writing, consider using more sophisticated alternatives like "therefore", "consequently", or "for this reason" to maintain a professional tone.

Linguistic Context

The phrase "That's why" functions as a causal connector, linking a preceding statement with its reason or consequence. As Ludwig AI confirms, it's used to explain the reason for something. It introduces the result or conclusion derived from the initial premise.

Expression frequency: Very common

Frequent in

News & Media

39%

Science

58%

Formal & Business

1%

Less common in

Encyclopedias

0%

Wiki

0%

Reference

0%

Ludwig's WRAP-UP

"That's why" is a versatile and common causal connector used to explain the reason or consequence of a statement. As Ludwig AI notes, it is grammatically correct and suitable for various contexts, although more formal alternatives may be preferred in academic or highly professional writing. Analysis of example sentences reveals its prevalence in news, media, and scientific sources, highlighting its adaptability. While it's a very common phrase, being mindful of the writing context and exploring alternatives like "therefore" or "consequently" can enhance writing precision and formality.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

This is why

Almost identical but can set a slightly different tone in some contexts.

That's the reason why

A more verbose but common variant, adding slight emphasis.

For this reason

More formal and emphasizes the justification for something.

That is the reason

Similar in meaning, slightly more emphatic.

As a result

Highlights the outcome or effect of a preceding action or situation.

Therefore

A formal and direct way to indicate a logical consequence.

Accordingly

Implies that an action or decision is made in response to a preceding situation.

Consequently

Similar to "therefore" but often used to emphasize the result or outcome.

Thus

Another formal way to indicate a logical consequence or conclusion.

Hence

A more formal and somewhat archaic term for "therefore".

FAQs

How to use "That's why" in a sentence?

"That's why" is used to indicate the reason or cause for something. For example, "I was feeling tired, "that's why" I went to bed early."

What can I say instead of "That's why"?

You can use alternatives like "therefore", "consequently", or "for this reason" depending on the context.

Which is correct, "That's why" or "That is why"?

Both "That's why" and "That is why" are grammatically correct. "That's why" is a contraction and is more commonly used in informal contexts, while "That is why" is slightly more formal.

What's the difference between "That's why" and "Because"?

"That's why" is used to introduce the consequence or result, while "Because" is used to introduce the reason or cause. For example, "I'm tired; "that's why" I'm going to bed" (consequence), versus "I'm going to bed "because" I'm tired" (reason).