Introduction
When you want to say “because” in Japanese, you probably immediately think of words like から (kara), ので (node), or ～んです (ndesu).
However, there is another very common grammar point used in daily conversation and business settings to express reasons, especially when you need to make an excuse or apologize:
～ものだから / ～もんだから = because (with a nuance of apology or explanation)
Let’s explore how to use this grammar point to soften your explanations and sound more empathetic and natural in Japanese!
1. Meaning and Nuance
While ～ものだから translates to “because,” it carries a very specific emotional nuance. It is primarily used to state personal reasons or causes, particularly in situations involving apologies (お詫び) or declining an invitation (断り).
Using this grammar conveys a feeling of “I’m sorry,” “It’s unfortunate, but…” or “I couldn’t help it because…” It helps you explain your circumstances without sounding overly defensive or blunt.
Formality Levels
The form changes depending on who you are talking to:
- ～ものですから (mono desu kara): Polite and formal. Use this with teachers, bosses, or in business settings.
- ～ものだから (mono dakara): Casual but slightly standard. Used with friends or family.
- ～もんだから (mon dakara): Very casual, spoken Japanese. Often used in relaxed conversations.
～もので (mono de) / ～もんで (mon de)
Very often, Japanese people will drop the “kara/su kara” and simply end the sentence with ～もので or ～もんで. This creates a trailing-off effect, leaving the apology unspoken but clearly understood.
Example: すみません、少し体調が悪いもので… (Sorry, I’m not feeling very well, so… [implied: I will go home early]).
2. Formation
This grammar point attaches to the Plain Form (普通形), but you need to be careful with な-adjectives and Nouns in the present affirmative tense.
| Word Type | Rule | Example |
|---|---|---|
| Verb | Plain Form + ものだから | 熱があったものだから (Because I had a fever) |
| い-adjective | Plain Form + ものだから | お腹が痛かったものだから (Because my stomach hurt) |
| な-adjective | Present Affirmative: Change だ to な Other tenses: Plain form | 不便なものだから (Because it is inconvenient) |
| Noun | Present Affirmative: Change だ to な Other tenses: Plain form | 子供なものだから (Because they are a child) |
3. Important Rule
Objective vs. Subjective
Because ～ものだから focuses on personal excuses and feelings, it cannot be used for objective facts, logical reasoning, or natural phenomena. In those cases, you must use から or ので.
- ✅ この飛行機は1時間に300キロ飛ぶから / ので、2時間で空港に着く。
(Because this plane flies 300km per hour, it will arrive at the airport in 2 hours.) - ❌ この飛行機は1時間に300キロ飛ぶものだから、2時間で空港に着く。
No Commands, Requests, or Intentions
Because this grammar is meant for explaining personal circumstances and seeking understanding, the main clause (the second half of the sentence) cannot contain commands, prohibitions, or strong personal volition (like “let’s do…”). For those, you must use から.
- ❌ 雨なものだから、傘を持っていきなさい。
- ✅ 雨だから、傘を持っていきなさい。(It’s raining, so take an umbrella.)
4. Example Sentences
Let’s look at how this is used in context, starting with formal situations and moving to casual ones.
Formal Situations (～ものですから)
A：どうして遅刻したんですか。
B：電車が遅れたものですから。
Why were you late? -> Because the train was delayed. (Apologetic nuance)
体の調子が悪いものですから、会社を休みました。
Because I wasn’t feeling well, I took the day off from work.
お金がないものですから、休日もアルバイトをしています。
Since I don’t have much money, I work part-time even on my days off.
Casual Situations (～ものだから / ～もんだから)
A：一緒に食事に行かない？
B：ごめん、今日はちょっと。忙しいもんだから。
Want to go eat together? -> Sorry, not today. I’m busy, you see. (Softening the rejection)
スマホが壊れたもんだから、友達に連絡できない。
Because my smartphone broke, I can’t contact my friends.
吉田さん、彼氏とけんかしているものだから、機嫌が悪いですね。
Ms. Yoshida is in a bad mood because she had a fight with her boyfriend.
5. Related grammar
～から
～から is a popular, casual expression to say “because.”
Example: JLPTの試験があるから、勉強します。= Because I have the JLPT exam, I will study.
だから
だから is a conjunction, similar to “so / therefore.”
It connects two sentences:
日本語はおもしろいです。だから、日本語を勉強しています。
Japanese is interesting. So, I study Japanese.
This is different from 〜から, which attaches directly to the word before it.
Let’s compare these patterns:
- 日本語はおもしろいです。だから、日本語を勉強しています。
(Conjunction: two sentences → “Therefore / So”) - 日本語はおもしろいですから、日本語を勉強しています。
(long form of おもしろい + から) - 日本語はおもしろいから、日本語を勉強しています。
(short form of おもしろい + から) - 日本語はおもしろいから、日本語を勉強してる。
(Casual + spoken contraction)
～ので
～ので is a softer, more polite way to say “because.”
While both ので and から mean “because,” they differ in tone and level of formality.
- から is more casual and is commonly used in everyday spoken language.
- It can sound more direct and expresses the speaker’s subjective reason.
- ので is generally more polite and formal.
- It is used in both spoken and written language, and it gives a softer, more objective impression.
Because of these differences:
- With friends, classmates, or family, から is far more common.
- With teachers, bosses, or people of higher status, ので often sounds more appropriate and natural.
Compare:
- 時間がないから、行かない。= I’m not going because I don’t have time. (casual)
- 時間がないので、行きません。= Since I don’t have time, I won’t go. (polite)
～んです
Use 〜んです when:
- Explaining a situation
- Answering a “why” question
- Provide additional information
Example:
- 今日は忙しいんです。= Actually, I’m busy today. (In response to a dinner invitation from a colleague)
- A: どうして遅刻したんですか。= Why were you late?
B: ごめんなさい、バスが遅れたんです。= I’m sorry, the bus was delayed. - A: すてきな車ですね。= Nice car.
B: 父の（車）なんです。= Actually, it’s my father’s.
Compare: ～んです vs. ～ものだから
While both can be used to explain a situation, ～ものだから sounds much more like an excuse and emphasizes that the situation was unavoidable.
- バスが遅れたんです。(The bus was delayed. -> Simple explanation/fact.)
- バスが遅れたものだから。(It’s because the bus was delayed… -> Apologetic, implied: “I couldn’t help being late.”)
FAQ
- QCan I use commands or requests after ～ものだから?
- A
No, you cannot. Because this grammar is meant for explaining personal circumstances and seeking understanding, it sounds unnatural to follow it with commands (do this), prohibitions (don’t do this), or strong volition. For commands, use から instead.
Example: It’s raining, so take an umbrella with you.
- ❌ 雨なものだから、傘を持っていきなさい。
- ✅ 雨だから、傘を持っていきなさい。
- QCan I use ～ものだから for positive reasons or boasting?
- A
Generally, no. ～ものだから has a built-in nuance of apologizing, explaining a failure, or justifying why something couldn’t be helped. If you use it for a positive reason, it will sound unnatural. Stick to using から or ので for positive or neutral reasons.
- QCan I use this grammar in business emails?
- A
Yes, the polite form ～ものですから (mono desu kara) is excellent for business emails when you need to gently explain a delay, decline an offer, or make a mild excuse.
Example: 本日は立て込んでいるものですから、明日お返事いたします。= I am quite tied up today, so I will reply tomorrow.
- QIs it okay to end a sentence completely with ～ものだから?
- A
Yes! In spoken Japanese, it is very common to explain your reason and just trail off, letting the listener fill in the blank. Example:
A: 「どうして食べないの？」(Why aren’t you eating?)
B: 「お腹がいっぱいなもんだから…」(Because I’m full, you see…)
Conclusion
Using ～ものだから / ～もんだから is a fantastic way to level up your Japanese and navigate social situations smoothly. Keep these main points in mind:
- Meaning: Expresses personal reasons or causes, especially for excuses or apologies.
- Politeness: Use ～ものですから for superiors/business, and ～ものだから/もんだから for casual chats.
- Rule: Do not use it for objective facts or follow it with commands/requests.
Rather than just saying “I was late,” saying 電車が遅れたものですから (Because the train was delayed…) shows that you feel bad about it and are politely explaining the situation. Give it a try next time you need to apologize or softly decline an invitation!
