That is why

USAGE SUMMARY

"that is why" is a valid phrase in written English.
It is used to explain the reason behind something, often as a result of the previous statement. For example: I can't make it to the concert; that is why I won't be able to join you.

✓ Grammatically correct

News & Media

Formal & Business

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

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

"That is why you do art.

The New York Times

That is why I am doing this.

The Guardian

Expert writing Tips

Best practice

Vary your sentence structure by occasionally replacing "That is why" with synonyms like "therefore" or "as a result" to avoid repetition and enhance readability.

Common error

Avoid using "That is why" when the causal relationship is already implied or when the sentence structure becomes overly convoluted. Overuse can make your writing sound repetitive or simplistic.

Linguistic Context

The primary grammatical function of "That is why" is to serve as a causal connector. It explicitly links a preceding statement to its consequence or explanation, providing a clear indication of cause and effect. As Ludwig AI confirms, the phrase is valid and well-understood. Examples from Ludwig illustrate its use in various contexts, providing a direct link between cause and result.

Expression frequency: Very common

Frequent in

News & Media

79%

Formal & Business

15%

Science

3%

Less common in

Encyclopedias

1%

Wiki

1%

Reference

1%

Ludwig's WRAP-UP

In summary, "That is why" is a very common causal connector used to explicitly link a statement to its consequence or explanation. Ludwig AI confirms that it's a valid phrase, widely used across various contexts, especially in news and media. The analysis shows that while grammatically correct and versatile, varying sentence structure and avoiding overuse can enhance writing quality. Consider using alternatives like "therefore" or "as a result" to maintain clarity and avoid repetition.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

For this reason

A more emphatic way of stating the cause or justification for something.

That's the reason

An informal alternative emphasizing the cause.

As a result

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

Therefore

A more formal single-word conjunction indicating a logical consequence.

This is the reason why

A slightly more elaborate way of introducing the explanation.

Thus

A concise and formal term indicating a result or conclusion.

Consequently

Similar to 'therefore' but emphasizes the result or effect of something.

Hence

A formal term indicating a logical consequence or inference.

Accordingly

Implies that something is done in a way that is appropriate for the situation.

It follows that

A more formal expression indicating a logical deduction.

FAQs

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

"That is why" is used to indicate a direct consequence or reason for something. For example, "The store was closed; "that is why" I couldn't buy milk."

What are some alternatives to "That is why"?

You can use alternatives such as "therefore", "consequently", or "as a result" to vary your writing.

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

Yes, it is grammatically correct to start a sentence with "That is why", especially to emphasize the causal relationship being explained. However, overuse might make your writing sound repetitive.

What is the difference between "That is why" and "Because"?

"That is why" introduces the consequence or result, whereas "because" introduces the reason or cause. For example, "I was late because the traffic was heavy" (cause), and "The traffic was heavy; "that is why" I was late" (consequence).