Japanese - Reasons

Lesson 39 of 168

Two colleagues talking about reasons in Japanese — polite phrases for explaining causes and decisions.

Goal: Ask and explain causes politely

Free Japanese lessons with guided practice, audio, and speaking support.

Ready to explain why things happen? In this B1 lesson we'll practice asking about causes and giving clear reasons. Have fun — the more you say these aloud, the more natural they feel!

Level B1: This lesson focuses on conversational phrases for giving and checking reasons — asking what caused something, confirming reasons, and explaining decisions or problems. You'll hear and repeat common polite frames like だから___んですか。(Dakara ___n desu ka.) and ___ことにしました。(___ koto ni shimashita.), then practice with short quizzes and speaking prompts. (CEFR-aligned)

After this lesson you'll be able to:

  • Be able to ask about causes politely (e.g. 何が原因で___んですか。 (Nani ga gen’in de ___n desu ka.))
  • Give one or more reasons using phrases like 理由の一つは、___ことです。 (Riyū no hitotsu wa, ___ koto desu.)
  • Confirm and explain decisions with ___ことにしました。 (___ koto ni shimashita.) and negative explanations with ___ませんでした。___からです。
A workplace scene in Japan where someone explains why they decided to move — visualizing reason and decision phrases in Japanese.

Ready? Let's go!

When you tap play on phrases, we track your progress through this lesson.

1. Reading + Listening Practice

Hear core phrases, repeat aloud.

だから___んですか。

Dakara ___n desu ka.

Is that why ___?

Meaning: Is that why ___?

When to use: Use to confirm a reason you just heard. Put a plain-form clause in the blank (e.g. だから遅れたんですか。).

Tip: Don't confuse this with simply saying だから—you need the plain-form reason before んですか to confirm it.

だから遅れたんですか。

Dakara okureta n desu ka.

Is that why you were late?
だから体調が悪かったんですか。

Dakara taichō ga warukatta n desu ka.

Is that why you were feeling unwell?

___ことにしました。___が理由です。

___ koto ni shimashita. ___ ga riyū desu.

I decided to ___ because of ___.

Meaning: I decided to ___ because of ___.

When to use: First blank takes a verb in plain form turned into ～ことにしました; second blank is the reason (noun or short phrase). You can also say the reason first with ～があったので、～ことにしました。

引っ越すことにしました。仕事の都合が理由です。

Hikkosu koto ni shimashita. Shigoto no tsugō ga riyū desu.

I decided to move. Work schedule is the reason.
習い事をやめることにしました。時間がないのが理由です。

Naraigoto o yameru koto ni shimashita. Jikan ga nai no ga riyū desu.

I decided to stop lessons. The reason is I don't have time.

___ませんでした。___からです。

___masen deshita. ___ kara desu.

I didn't ___ because I was ___.

Meaning: I didn't ___ because I was ___.

When to use: Use to explain a negative action. The first blank is the verb in its ます-form (negative) phrase, then give the reason in plain form (e.g. 疲れていたからです).

Tip: Beginners sometimes put a polite reason in the wrong form; the reason after から is usually plain past or plain present (e.g. 忙しかったからです).

連絡しませんでした。忙しかったからです。

Renraku shimasen deshita. Isogashikatta kara desu.

I didn't contact (them). I was busy.
参加しませんでした。体調が悪かったからです。

Sanka shimasen deshita. Taichō ga warukatta kara desu.

I didn't participate. I was feeling unwell.

理由の一つは、___ことです。

Riyū no hitotsu wa, ___ koto desu.

One reason is that ___.

Meaning: One reason is that ___.

When to use: Use this to introduce one reason among several. Put a plain-form clause in the blank (e.g. 理由の一つは、時間がないことです).

理由の一つは、通勤時間が長いことです。

Riyū no hitotsu wa, tsūkin jikan ga nagai koto desu.

One reason is that commute time is long.
理由の一つは、予算が足りないことです。

Riyū no hitotsu wa, yosan ga tarinai koto desu.

One reason is that the budget is insufficient.

だから___んです。

Dakara ___n desu.

That's why I ___.

Meaning: That's why I ___.

When to use: Use to connect a previous explanation to a result or action. Put a plain-form clause in the blank (e.g. だから行かなかったんです).

だから行かなかったんです。

Dakara ikanakatta n desu.

That's why I didn't go.
だから買えなかったんです。

Dakara kaenakatta n desu.

That's why I couldn't buy it.

聞いた理由は、___からです。

Kiita riyū wa, ___ kara desu.

The reason I ask is ___.

Meaning: The reason I ask is ___.

When to use: Use this to explain why you are asking a question. The phrase often uses past-tense form 「聞いた理由」 naturally; put a plain-form reason in the blank.

聞いた理由は、心配だったからです。

Kiita riyū wa, shinpai datta kara desu.

The reason I asked is that I was worried.
聞いた理由は、締め切りが近かったからです。

Kiita riyū wa, shimekiri ga chikakatta kara desu.

The reason I asked is that the deadline was near.

何が原因で___んですか。

Nani ga gen’in de ___n desu ka.

What led to ___?

Meaning: What led to ___?

When to use: Ask about the cause of a situation. Put a plain-form clause in the blank (e.g. 何が原因でこうなったんですか). For softer talk, you can say どうして___んですか。

何が原因で事故が起きたんですか。

Nani ga gen’in de jiko ga okita n desu ka.

What caused the accident?
何が原因で遅れたんですか。

Nani ga gen’in de okureta n desu ka.

What caused you to be late?

___が原因だったんですか。

___ ga gen’in dattan desu ka.

Was it due to ___?

Meaning: Was it due to ___?

When to use: Ask if a specific factor was the cause. Put the suspected cause (noun or phrase) in the blank followed by が自然です.

天気が原因だったんですか。

Tenki ga gen’in dattan desu ka.

Was it due to the weather?
システムのエラーが原因だったんですか。

Shisutemu no erā ga gen’in dattan desu ka.

Was it caused by a system error?

___と思ったので、___ました。

___ to omotta node, ___mashita.

I thought ___, so I ___.

Meaning: I thought ___, so I ___.

When to use: Put a plain-form thought in the first blank (___と思った) and a past polite action in the second (～ました). For example: 雨が降ると思ったので、車で行きました。

雨が降ると思ったので、車で行きました。

Ame ga furu to omotta node, kuruma de ikimashita.

I thought it would rain, so I went by car.
時間が足りないと思ったので、早めに出ました。

Jikan ga tarinai to omotta node, hayame ni demashita.

I thought there wouldn't be enough time, so I left early.

問題は、___ことでした。

Mondai wa, ___ koto deshita.

The problem was that ___.

Meaning: The problem was that ___.

When to use: Use this to state the cause of a problem. Put a plain-form clause in the blank (e.g. 問題は、時間がなかったことでした).

問題は、時間が足りないことでした。

Mondai wa, jikan ga tarinai koto deshita.

The problem was that there wasn't enough time.
問題は、書類が不完全だったことでした。

Mondai wa, shorui ga fukanzen datta koto deshita.

The problem was that the documents were incomplete.

理由はいくつかあります。

Riyū wa ikutsuka arimasu.

There are a few reasons.

Meaning: There are a few reasons.

When to use: Use this as a lead-in when you will explain multiple reasons. In casual speech you can say 理由はいくつかあるよ。

理由はいくつかあります。まず、予算の問題です。

Riyū wa ikutsuka arimasu. Mazu, yosan no mondai desu.

There are a few reasons. First, a budget issue.
理由はいくつかあります。時間と場所が主な理由です。

Riyū wa ikutsuka arimasu. Jikan to basho ga omona riyū desu.

There are a few reasons. Time and location are the main ones.

もう一つの理由は、___ことです。

Mō hitotsu no riyū wa, ___ koto desu.

Another reason is that ___.

Meaning: Another reason is that ___.

When to use: Use to add a second reason. Put a plain-form clause in the blank (or a noun alone with です).

もう一つの理由は、準備が不十分だったことです。

Mō hitotsu no riyū wa, junbi ga fujūbun datta koto desu.

Another reason is that preparation was insufficient.
もう一つの理由は、参加者が少ないことです。

Mō hitotsu no riyū wa, sankasha ga sukunai koto desu.

Another reason is that there were few participants.

2. Conversational Listening Practice

Hear phrases in a real mini-conversation.

Anna and David discuss why yesterday's meeting ended early.

Anna and David talking beside a meeting room: they ask what caused the meeting to end early and give several reasons in Japanese.

What are Anna and David talking about?

Portrait of David in a Japanese lesson dialogue

David

何が原因で会議が早く終わったんですか。

Nani ga gen’in de kaigi ga hayaku owatta n desu ka.

What caused the meeting to end early?

Portrait of Anna in a Japanese lesson dialogue

Anna

参加者が少なかったのが原因だったんです。

Sankasha ga sukunakatta no ga gen’in dattan desu.

It was because there were few participants.

Portrait of David in a Japanese lesson dialogue

David

聞いた理由は、急な用事があったからですか。

Kiita riyū wa, kyūna yōji ga atta kara desu ka.

Is the reason you heard that there were sudden errands?

Portrait of Anna in a Japanese lesson dialogue

Anna

はい、そうです。理由はいくつかあります。

Hai, sō desu. Riyū wa ikutsuka arimasu.

Yes. There are a few reasons.

Portrait of David in a Japanese lesson dialogue

David

もう一つの理由は何ですか。

Mō hitotsu no riyū wa nan desu ka.

What's another reason?

Portrait of Anna in a Japanese lesson dialogue

Anna

準備が不十分だったことです。だから短くなったんです。

Junbi ga fujūbun datta koto desu. Dakara mijikaku natta n desu.

The preparation was insufficient. That's why it got shortened.

3. Guided Practice

Quizzes and matching to lock in meaning.

Which Japanese phrase asks 'Is that why...?'

Which phrase means 'One reason is that ___.'?

Which phrase explains a negative action with a personal condition: 'I didn't ___ because I was ___.'?

Which phrase means 'I thought ___, so I ___.'?

I decided to quit my job. Family circumstances are the reason.

会社を辞める___。家庭の事情が理由です。

The train delay made me late for the meeting. What caused you to be late?

電車の遅延で会議に遅れました。何が原因で___んですか。

You look very tired. Is it because you worked late?

あなた、ずいぶん疲れているね。だから___んですか。

Match the core phrases

Match the extra phrases

4. Speaking Practice

Say phrases yourself (mic/recording).

Recording stays on your device only. Check speech uses your browser's speech tools when available.

Say this phrase out loud:

だから___んですか。

Dakara ___n desu ka.

Is that why ___?

Say this phrase out loud:

___ことにしました。___が理由です。

___ koto ni shimashita. ___ ga riyū desu.

I decided to ___ because of ___.

Say this phrase out loud:

___ませんでした。___からです。

___masen deshita. ___ kara desu.

I didn't ___ because I was ___.

Say this phrase out loud:

理由の一つは、___ことです。

Riyū no hitotsu wa, ___ koto desu.

One reason is that ___.

Say this phrase out loud:

だから___んです。

Dakara ___n desu.

That's why I ___.

Say this phrase out loud:

聞いた理由は、___からです。

Kiita riyū wa, ___ kara desu.

The reason I ask is ___.

Say this phrase out loud:

何が原因で___んですか。

Nani ga gen’in de ___n desu ka.

What led to ___?

Say this phrase out loud:

___が原因だったんですか。

___ ga gen’in dattan desu ka.

Was it due to ___?

Say this phrase out loud:

___と思ったので、___ました。

___ to omotta node, ___mashita.

I thought ___, so I ___.

Say this phrase out loud:

問題は、___ことでした。

Mondai wa, ___ koto deshita.

The problem was that ___.

Say this phrase out loud:

理由はいくつかあります。

Riyū wa ikutsuka arimasu.

There are a few reasons.

Say this phrase out loud:

もう一つの理由は、___ことです。

Mō hitotsu no riyū wa, ___ koto desu.

Another reason is that ___.