that is why

USAGE SUMMARY

"that is why" is a correct and usable phrase in written English.
You can use it to explain a cause or reason for something. For example, "The research has shown that many people suffer from anxiety, and that is why it is so important to take care of our mental health."

✓ Grammatically correct

News & Media

Human-verified examples from authoritative sources

Exact Expressions

60 human-written examples

That is why they left".

The Economist

That is why they exist.

Independent

That is why we care.

The New York Times

And that is why.

The New York Times - Arts

That is why.

The Washington Post

That is why Rapinoe revels in it.

The New York Times - Sports

That is why they are popular.

Independent

That is why catalysts are so important.

The Economist

That is why investors are piling in.

The Economist

That is why all this grumbling matters".

The New York Times

That is why the unemployment rate rose.

The Economist

Expert writing Tips

Best practice

Use "that is why" to clearly and directly explain the consequence of a preceding statement, ensuring a smooth flow of logic in your writing.

Common error

Avoid using "that is why" multiple times in close succession within a single paragraph; instead, vary your sentence structure by using synonyms like "therefore", "consequently", or "as a result" to maintain reader engagement and avoid redundancy.

Linguistic Context

The phrase "that is why" serves as a causal connector, linking a cause or reason presented in a previous statement to its resulting effect. As Ludwig AI confirms, this construction is grammatically sound and widely utilized. The examples from Ludwig clearly demonstrate its role in providing explanations and logical conclusions.

Expression frequency: Very common

Frequent in

News & Media

100%

Less common in

Formal & Business

0%

Science

0%

Encyclopedias

0%

Ludwig's WRAP-UP

In summary, "that is why" is a highly versatile phrase used to clearly establish a cause-and-effect relationship. Ludwig AI confirms its grammatical correctness and usability in various contexts. Its prevalence in news and media sources, and as observed from Ludwig's examples, indicates its wide acceptance and utility in explaining reasons or consequences. While it’s essential for clear communication, avoid overuse by employing synonyms such as "therefore" or "as a result" for stylistic variation. Keep in mind that while generally neutral in tone, it can be adapted in formal or informal context based on surrounding vocabulary. By keeping these points in mind, you can effectively use "that is why" to enhance clarity and logical flow in your writing.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

this is why

Slightly more emphatic, draws attention to the explanation.

that explains why

Focuses on clarification and understanding.

that's the reason

Informal phrasing, direct explanation.

for this reason

Emphasizes the preceding cause, slightly more formal.

as a result

Highlights the outcome of a previous action, neutral tone.

because of that

Highlights the causal relationship explicitly.

therefore

Single word expressing consequence, more formal.

consequently

Indicates a logical conclusion, more formal.

it follows that

Expresses a logical consequence, more formal and academic.

hence

Formal and somewhat archaic, indicating a logical deduction.

FAQs

How can I use "that is why" in a sentence?

"That is why" is used to indicate the consequence or result of a preceding statement. For example, "The company invested heavily in research and development; "that is why" their products are so innovative."

What are some alternatives to "that is why"?

You can use alternatives such as "therefore", "as a result", "consequently", or "for this reason" to express a similar relationship of cause and effect.

Is it correct to start a sentence with "that is why"?

Yes, it is grammatically correct to start a sentence with "that is why", especially when you want to emphasize the logical connection between the previous statement and the current one.

What's the difference between "that is why" and "because"?

"Because" introduces the reason or cause, while "that is why" introduces the result or consequence. For example, "Because it was raining, we stayed inside." versus "It was raining; "that is why" we stayed inside."