number one reason

USAGE SUMMARY

The phrase "number one reason" is correct and usable in written English. You can use it when emphasizing the most important reason for something. An example is: "The number one reason for our success is teamwork." Alternative expressions include "top reason," "primary reason," and "main reason."

✓ Grammatically correct

News & Media

Wiki

Science

Human-verified examples from authoritative sources

Exact Expressions

52 human-written examples

The number one reason for things going wrong is scale.

The Guardian - Tech

That's probably my number one reason for doing it actually – no internet.

The Guardian

Social media is the number one reason we use the internet.

The Guardian

Domestic violence remains the number one reason people become homeless in Australia.

The Guardian

The number one reason cited for food bank referral is cuts or delays to benefits, including sanctions and bedroom tax.

The Guardian - Opinion

It found that domestic violence remains the number one reason people – mainly women and children – become homeless.

The Guardian

Human-verified similar examples from authoritative sources

Similar Expressions

8 human-written examples

This is the number one-reason to be nice to the stepparent.

Huffington Post

"The number-one reason people put on weight is low self-worth.

Huffington Post

Indeed, work is the number-one reason people cut back on sleep.

Huffington Post

The number-one reason listed is "irreconcilable differences".

Huffington Post

The number-one reason older adults often refuse assistance is fear of losing control.

Huffington Post

Expert writing Tips

Best practice

Consider hyphenating the phrase as "number-one reason" when it acts as a compound modifier directly before the noun it describes, as seen in some professional publications.

Common error

Avoid combining the phrase with other superlative adjectives, such as "the number one main reason" or "the number one most important reason". Since "number one" already establishes the highest rank, adding "main" or "most important" is redundant and cluttering.

Linguistic Context

The phrase "number one reason" functions as a complex noun phrase where "number one" acts as an adjectival modifier indicating rank or priority. According to Ludwig AI, it is primarily used to isolate a single most significant cause from a potential list of many.

Expression frequency: Very common

Frequent in

News & Media

72%

Wiki

18%

Science

10%

Less common in

Academic

5%

Social Media

3%

Reference

2%

Ludwig's WRAP-UP

The phrase "number one reason" is an exceptionally useful tool for writers who need to highlight the most critical factor in a situation. Ludwig data confirms its widespread acceptance across high-authority journalism and digital media. While it is grammatically sound and universally understood, writers should be mindful of redundancy; avoid adding words like "main" to it. For highly formal academic or legal writing, consider more precise alternatives like "primary factor". Overall, it remains one of the most effective ways to introduce the most important point of an argument.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

primary reason

More formal and suitable for academic or business reports

single biggest reason

Adds extra emphasis on the scale of the reason

main factor

Shifts focus from a rationale to an influencing element

leading cause

Commonly used in medical, scientific or negative contexts

key driver

Frequent in business jargon to describe what pushes results

chief motivation

Emphasizes the internal drive or psychological reason

core explanation

Suggests a deeper, more fundamental level of understanding

principal justification

Higher level of formality used in legal or official defenses

top priority

Focuses on the importance of the item rather than just the logic

prime mover

An idiomatic way to describe the initial force behind a change

FAQs

How do I use "number one reason" in a sentence?

You can use it to lead an explanation, such as: "The "number one reason" for the delay was the weather."

What can I say instead of "number one reason" in a formal essay?

In formal contexts, it is often better to use "primary reason" or "principal factor" to maintain a professional tone.

Should I write "number 1 reason" or "number one reason"?

In most style guides, including APA and MLA, you should spell out the word "one" for small numbers, making ""number one reason"" the preferred choice.

Is it "number one reason" or "number-one reason"?

Both are acceptable. However, using a hyphen as in "number-one reason" is more technically correct when it functions as a compound adjective before a noun.