That's Why: Definition, Meaning, and Origin

Last Updated on
July 14, 2023

People often use the expression "that's why" in everyday conversations, showing a cause-and-effect relationship. It explains something already mentioned, like an action, event, or situation. This handy phrase also connects two different bits of information, adding context or a reason for a result or situation. You can use "that's why" in both serious discussions and casual chats, making it great for explaining things and helping others understand better in any conversation.

In short: 

  • It ties together two separate pieces of information to provide context or reason.
  • It emphasizes the importance of the preceding statement or action.

What Does "That's Why" Mean?

At its core, "that's why" connects a cause with an effect or a reason with a result. People usually use it after a statement to help explain the thinking or logic behind it. But remember, its meaning can change a bit depending on the situation.

  • You can use it to introduce the reason or cause for a specific outcome or as a linking word between two clauses or sentences. For example, "It was raining; that's why I took an umbrella."
  • You can also use 'that's why' as a standalone response to show that you agree with someone else's reasoning. For instance, if someone says, "It looks like it's going to rain today," you can respond, "That's why I brought an umbrella."

Where Does "That's Why" Come From?

The origin of “that’s why” is not very clear, but it seems to be a shortened form of “that is why” or “that is the reason why.” According to Google Ngram Viewer, the phrase “that is why” has been used in English books since the 16th century, while “that’s why” has been used since the 19th century. The phrase “that is the reason why” has been used since the 17th century, but it is considered redundant by some grammarians.

Historical Examples

"That's the reason why I had to embroider tulips, which I hate, on his slippers; because you are fond of tulips; that's why (throws the slippers on the floor) we go to the mountains during the summer, because you don't like the sea air; that's why my boy is named Eskil, because it's your father's name..."

- The Stronger by August Strindberg, 1889

"I was born so, and that's why never got married. Girls want somebody that acts just like somebody else. She was born lonesome, and she's married you. I don't know which of us got the worst of it.

- The Man Who Went With The Place by Margaret L. Knapp, 1901

10 Examples of "That's Why" in Sentences

Here are ten examples of "that's why" in sentences and different contexts:

  • They promised each other, "till death do us part." That's why their bond is unbreakable.
  • That's why I study hard; I want to get into a good university.
  • He almost never attends the morning sessions, that's why his understanding of the subject is lagging.
  • They missed their flight; that's why they were late.
  • I didn't set the alarm last night and overslept this morning; that's why.
  • That's why we need a break: we've been working non-stop.
  • Tuesday's child is full of grace; that's why she's the favorite daughter.
  • I fell head over heels for the city's vibrant culture. That's why I decided to move here.
  • That's why I always carry an umbrella; you never know when it might rain.
  • I don't beg for love. There are plenty of fish in the sea; that's why.

Examples of "That's Why" in Pop Culture

Due to its versatile nature, the phrase "that's why" often appears in various forms of media, including movies, TV shows, and music.

Some notable examples are:

  • The song "That's Why (You Go Away)" by Michael Learns to Rock uses the phrase to express the reason behind the singer's heartbreak.
  • "That's Why We Tried to Find You" is a 2021 film featuring Tiffany Holloway and Michael Sparko.
  • "I Guess That's Why They Call It the Blues" is a song by Elton John, known for his powerful and emotive performances. Released in 1983, the song explores the complexities of love and heartache.
  • "I Love Her, That's Why!: An Autobiography" is a 2017 book by George Burns and Cynthia Hobart Lindsay. In this captivating autobiography, George Burns, a legendary comedian and entertainer, shares his personal journey and reflections on his life and career.

Other/Different Ways to Say "That's Why"

While "that's why" is a standard phrase, several synonyms and similar expressions in English convey the same message.

Here are a few examples:

  • Consequently
  • As a result
  • Therefore
  • For this reason
  • Thus
  • Hence
  • Due to
  • Because of
  • As a consequence
  • This is why

10 Frequently Asked Questions About "That's Why":

  • What does "that's why" mean?

It's a phrase used to connect a cause and effect or to explain the reason behind a situation or event.

  • What is the origin of "that's why"?

The exact origin of "that's why" is unclear due to its widespread use and simple nature. However, it's a universally understood concept, expressing logical reasoning in many languages.

  • Can I use it as a standalone response?

Yes, "that's why" can be used as a standalone response to signify agreement with a provided reason.

  • What are some synonyms of "that's why"?

Some synonyms include "hence," "therefore," "consequently," "as a result," and "for this reason."

  • Can I start a sentence with "that's why" followed by a comma?

No, it is grammatically incorrect to start a sentence with "that's why" followed immediately by a comma. "That's why" should be followed by a complete clause or sentence. A comma can be used if "that's why" is not at the very beginning. 

  • Is it okay to use it in formal writing?

Yes, although alternatives like "hence" or "therefore" are often preferred for their more formal tone.

  • Can I use it instead of "because"?

While both "that's why" and "because" express causality, they are not always interchangeable. "That's why" usually follows a statement or event, while "because" typically precedes the reason or explanation. Take a look at these examples: "I was tired, that's why I went to bed early." "I went to bed early because I was tired."

  • Can the phrase "that's why" be used at the beginning of a sentence?

Yes, "that's why" can be used at the start of a sentence to emphasize the cause-effect relationship.

  • Can I use it to express a future outcome?

Yes, "that's why" can be used to express a future outcome, as long as the cause-effect relationship is clear. For example, "I have a big presentation tomorrow, and that's why I'm preparing so diligently today."

  • Can "that's why" be replaced by a semicolon?

In certain situations, a semicolon can replace "that's why" to connect two closely related independent clauses.

Final Thoughts About "That's Why"

“That’s why” is a common and well-understood phrase that explains or justifies something. You can use it in both informal and formal contexts, and it has a variety of synonyms. It can appear after a statement to emphasize the reason or explanation just given, especially in response to a statement or question using the word “why." The meaning of the phrase depends on the context and the tone of the speaker.

Here's a quick summary:

  • "That's why" explains or justifies a situation, event, or action.
  • It functions similarly to a conjunction connecting two sentences or clauses.
  • The phrase can also serve as a standalone response.
  • It has numerous synonyms, including "hence," "therefore," and "consequently."

The expression "that's why" may seem straightforward, but understanding its nuances can greatly enhance your language proficiency and communication skills.

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