Common Mistakes When Using ‘therefore’ in a Sentence

Many English learners use therefore to show a logical result, but they often place it incorrectly, overuse it, or confuse it with other connectors. The most common mistakes include putting therefore in the wrong position, using it without proper punctuation, and treating it like a simple conjunction such as so. This guide explains exactly how to use therefore correctly in formal and informal writing, with clear examples and practical fixes.

Quick Answer: How to Use ‘therefore’ Correctly

Therefore is a conjunctive adverb that means “for that reason” or “as a result.” It connects two independent clauses and usually requires a semicolon or period before it and a comma after it. For example: “The experiment failed; therefore, we must repeat it.” In informal writing, you can also use it at the beginning of a sentence: “Therefore, we decided to leave early.” Do not use therefore to join two clauses without punctuation, and do not use it in every sentence—it is best for formal contexts like academic essays, reports, and professional emails.

Understanding the Role of ‘therefore’

Therefore signals a cause-and-effect relationship. It tells the reader that the second idea follows logically from the first. Unlike so, which is a coordinating conjunction, therefore is an adverb and follows different punctuation rules. It is more formal than so and is common in academic writing, business reports, and legal documents. In everyday conversation, therefore can sound stiff, so speakers often use so or that’s why instead.

Formal vs. Informal Tone

Use therefore in formal writing: research papers, official emails, presentations, and professional reports. In informal contexts—text messages, casual emails, or friendly conversation—choose so, thus, or that’s why. For example:

• Formal: The data was incomplete; therefore, the analysis could not proceed.
• Informal: The data was incomplete, so we couldn’t finish the analysis.

Comparison Table: ‘therefore’ vs. Common Alternatives

Natural Examples of ‘therefore’ in Sentences

Here are correct examples in different contexts. Notice the punctuation and position of therefore.

Academic Writing

• The sample size was too small; therefore, the results are not statistically significant.
• Several participants withdrew from the study. Therefore, we adjusted the timeline.
• The theory has not been tested in a real-world setting; therefore, its validity remains uncertain.

Business and Professional Emails

• Our supplier has increased prices by 15%. Therefore, we must revise our budget.
• The client requested additional features; therefore, the project deadline has been extended.
• We did not receive the signed contract by the deadline. Therefore, the offer is no longer valid.

Everyday Conversation (Less Common)

• I missed the bus; therefore, I was late for the meeting.
• She has a fear of heights; therefore, she avoids tall buildings.

Common Mistakes with ‘therefore’

Mistake 1: Using ‘therefore’ as a conjunction

Incorrect: “He studied hard therefore he passed the exam.”
Correct: “He studied hard; therefore, he passed the exam.”
Therefore is not a conjunction like and or so. It cannot join two clauses without a semicolon or period.

Mistake 2: Missing comma after ‘therefore’

Incorrect: “The evidence was clear therefore the jury reached a verdict.”
Correct: “The evidence was clear; therefore, the jury reached a verdict.”
Always place a comma after therefore when it introduces the second clause.

Mistake 3: Overusing ‘therefore’

Incorrect: “The project was delayed. Therefore, we missed the deadline. Therefore, we lost the client. Therefore, we need a new strategy.”
Better: “The project was delayed, so we missed the deadline. Consequently, we lost the client and need a new strategy.”
Using therefore in every sentence sounds repetitive and unnatural. Vary your connectors.

Mistake 4: Using ‘therefore’ in casual conversation too often

Incorrect (in a text message): “I’m tired therefore I’m going to bed.”
Natural: “I’m tired, so I’m going to bed.”
In informal settings, so or that’s why sounds more natural.

Mistake 5: Placing ‘therefore’ in the wrong position

Incorrect: “The results, therefore, were inconclusive.” (This is actually acceptable but can be confusing if overused.)
Better: “The results were inconclusive; therefore, we repeated the experiment.”
Mid-sentence placement is possible but less common. Most writers place therefore at the beginning of the second clause for clarity.

Better Alternatives to ‘therefore’

If you find yourself using therefore too often, try these alternatives:

• So – for informal or neutral writing: “It was raining, so we stayed inside.”
• Thus – for very formal writing: “The theory was disproven; thus, a new hypothesis was needed.”
• Consequently – for emphasizing a direct result: “The budget was cut; consequently, the program ended.”
• As a result – for clear cause and effect: “The server crashed. As a result, all data was lost.”
• For this reason – for explaining a logical conclusion: “The patient showed no improvement. For this reason, the treatment was changed.”

When to Use ‘therefore’ (and When Not To)

Use ‘therefore’ when:

• You are writing a formal document (essay, report, research paper).
• You need to show a clear logical conclusion.
• You want to sound precise and professional.
• You are connecting two complete thoughts that have a cause-effect relationship.

Avoid ‘therefore’ when:

• You are texting or chatting with friends.
• You are writing a creative story (it can sound stiff).
• You have already used it in the previous sentence.
• The connection between ideas is obvious without a connector.

Mini Practice: 4 Questions with Answers

Test your understanding. Choose the correct option or rewrite the sentence.

Question 1: Which sentence is correct?
a) The weather was bad therefore the flight was cancelled.
b) The weather was bad; therefore, the flight was cancelled.
c) The weather was bad, therefore the flight was cancelled.

Answer: b) The weather was bad; therefore, the flight was cancelled.

Question 2: Rewrite this sentence using therefore correctly: “The company lost money they had to lay off staff.”

Answer: “The company lost money; therefore, they had to lay off staff.” OR “The company lost money. Therefore, they had to lay off staff.”

Question 3: Which alternative is best for an informal email to a colleague?
a) The meeting was rescheduled; therefore, please update the calendar.
b) The meeting was rescheduled, so please update the calendar.

Answer: b) The meeting was rescheduled, so please update the calendar.

Question 4: Is this sentence correct? “Therefore we must act now.”

Answer: It is acceptable in very informal writing, but in formal writing, add a comma: “Therefore, we must act now.”

Frequently Asked Questions

1. Can I start a sentence with ‘therefore’?

Yes, you can. When you start a sentence with therefore, place a comma after it. For example: “Therefore, we decided to change the approach.” This is common in both formal and informal writing.

2. What is the difference between ‘therefore’ and ‘so’?

Therefore is a conjunctive adverb and is more formal. It requires a semicolon or period before it. So is a coordinating conjunction and is less formal. It requires only a comma before it. Example: “I was tired, so I went to bed.” vs. “I was tired; therefore, I went to bed.”

3. Can I use ‘therefore’ in the middle of a sentence?

Yes, but it is less common. When used in the middle, it is usually set off by commas. For example: “The results, therefore, were not reliable.” This placement can add emphasis but may interrupt the flow. Most writers prefer to put therefore at the beginning of the second clause.

4. Is ‘therefore’ too formal for everyday writing?

It depends on the context. In academic essays, business reports, and formal emails, therefore is appropriate. In casual emails, text messages, or personal notes, so or that’s why sounds more natural. Use your judgment based on your audience and purpose.

Final Tips for Using ‘therefore’

• Always check punctuation: semicolon or period before, comma after.
• Do not use therefore more than once in a paragraph unless necessary.
• In formal writing, therefore is a strong choice; in casual writing, choose so.
• Read your sentence aloud. If it sounds too stiff, consider a different connector.
• Practice by rewriting sentences from your own writing using therefore correctly.

For more help with academic words and sentence structure, explore our Common Usage Mistakes section or visit our FAQ page. If you have questions about this guide, feel free to contact us.