原因在于...
The reason is...
Literally: Reason (原因) lies (在于) ...
Use it to sound logical and professional when explaining the root cause of a situation.
In 15 Seconds
- A more polished way to say 'the reason is'.
- Perfect for explaining problems in a logical way.
- Best used in professional or serious personal conversations.
Meaning
Think of this as a slightly more sophisticated way to say 'because.' It's like saying 'the reason lies in' or 'the cause is actually' when you want to sound clear and logical.
Key Examples
3 of 6Explaining a mistake to a boss
这次计划失败了，原因在于准备不足。
The plan failed this time; the reason lies in insufficient preparation.
Discussing health with a friend
你总是觉得累，原因在于你运动太少。
You always feel tired; the reason is that you exercise too little.
Texting about a late reply
刚才没回信息，原因在于手机没电了。
I didn't reply just now; the reason was my phone died.
Cultural Background
This expression reflects the Chinese preference for formal logic in explanatory speech. It gained popularity in modern professional environments as a way to provide objective analysis. It bridges the gap between everyday speech and academic writing.
The 'Drop-In' Trick
If you're about to say '因为', try swapping it for '原因在于' to instantly sound 20% more professional.
Don't Double Up
Avoid saying '因为原因在于'. That's like saying 'Because the reason is because'. Just pick one!
In 15 Seconds
- A more polished way to say 'the reason is'.
- Perfect for explaining problems in a logical way.
- Best used in professional or serious personal conversations.
What It Means
原因在于 is your go-to phrase for explaining the 'why' behind a situation. It is more structured than the basic 因为. It points directly to the heart of the matter. Use it when you want to sound like you've really thought things through.
How To Use It
Place it right after the problem or situation you just mentioned. It acts as a bridge. For example: 'I am tired. 原因在于 I stayed up late.' It follows a simple pattern: [Result/Situation] + 原因在于 + [The Reason]. It feels very organized and satisfying to say.
When To Use It
You can use this in a business meeting to sound professional. Use it when explaining why a project is late. It also works great when you're giving advice to a friend. It makes your explanation feel more authoritative and grounded. It’s perfect for writing emails or essays too.
When NOT To Use It
Don't use it for tiny, obvious things. If someone asks why you're eating, don't say 原因在于 I'm hungry. That sounds like a robot trying to be human. Avoid it in high-energy, fast-paced slang sessions. It’s a bit too 'neat' for a shouting match or a rowdy party.
Cultural Background
Chinese culture values logical flow and 'face' in communication. Using 原因在于 helps you provide a reason without sounding defensive. It shifts the focus from 'me' to the 'reason' itself. This objective tone is highly respected in professional and academic circles. It shows you are a person of reason and logic.
Common Variations
You might hear 原委在于 for more complex backstories. Or 症结在于 when talking about a specific 'knot' or problem. For a shorter version, people sometimes just use 在于. But 原因在于 remains the most balanced and popular choice for intermediate speakers.
Usage Notes
This phrase sits comfortably in the 'neutral to formal' range. It is highly effective in persuasive speaking and writing to create a sense of logical inevitability.
The 'Drop-In' Trick
If you're about to say '因为', try swapping it for '原因在于' to instantly sound 20% more professional.
Don't Double Up
Avoid saying '因为原因在于'. That's like saying 'Because the reason is because'. Just pick one!
Logical Face
In China, being seen as '讲道理' (jiǎng dàolǐ - reasonable) is a high compliment. This phrase helps you earn that reputation.
Examples
6这次计划失败了，原因在于准备不足。
The plan failed this time; the reason lies in insufficient preparation.
Using this phrase makes the speaker sound analytical rather than just making excuses.
你总是觉得累，原因在于你运动太少。
You always feel tired; the reason is that you exercise too little.
It sounds like helpful, objective advice.
刚才没回信息，原因在于手机没电了。
I didn't reply just now; the reason was my phone died.
A bit formal for a text, but very clear.
它不理你，原因在于你没给它零食。
It's ignoring you; the reason is you didn't give it snacks.
Applying a formal structure to a silly situation creates a funny contrast.
我们分手了，原因在于性格不合。
We broke up; the reason was personality incompatibility.
Provides a clear, final explanation for a sensitive topic.
这家店生意很好，原因在于食材很新鲜。
This shop does great business; the reason is the ingredients are very fresh.
A standard way to provide a logical observation.
Test Yourself
Choose the best phrase to complete the logical explanation.
他中文进步很快，___ 他每天都练习。
The sentence explains the cause of his fast progress, making 'the reason is' the best fit.
Complete the professional excuse.
项目推迟了，___ 资金还没到位。
While '因为' is grammatically correct, '原因在于' is more professional for a project delay context.
🎉 Score: /2
Visual Learning Aids
Formality Spectrum of Explaining 'Why'
Simple and direct
因为 (yīnwèi)
Balanced and clear
原因在于 (yuányīn zàiyú)
Academic or legal
究其原因 (jiū qí yuányīn)
Where to use 原因在于
Work Meeting
Explaining a drop in sales
Doctor Visit
Discussing symptoms
Serious Talk
Discussing relationship issues
Writing
Writing a blog or essay
Frequently Asked Questions
10 questionsNot exactly. 因为 is a conjunction like 'because,' while 原因在于 is more like 'the reason lies in.' It's slightly more formal.
Usually, you state the result first, then use 原因在于. For example: 他很成功，原因在于他很努力。
It's fine for serious topics with friends, but might sound a bit stiff if you're just talking about what to eat for lunch.
在于 means 'to lie in' or 'to consist of.' It points to the essence of something.
Yes! It is perfect for professional emails where you need to explain a situation clearly.
The most common mistake is adding 是 (is) before 在于. You don't need it; 在于 already acts as the verb.
Yes, you can sometimes just use 在于 if the context of 'reason' is already clear from the previous sentence.
It can if overused, but in a logical discussion, it sounds smart and clear rather than 'bookish'.
Absolutely! You can use it to explain success just as easily as you use it to explain failure.
It is standard Mandarin used throughout all regions of China, especially in media and business.
Related Phrases
归根结底
In the final analysis / at the end of the day
主要是因为
Mainly because
其原因如下
The reasons are as follows (very formal)
难怪
No wonder (informal way to acknowledge a reason)
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