JLPT N3Written, formalEssays, presentations

なぜなら～からthe reason is that…

You say what you think, then give the reason in a sentence of its own. なぜなら opens the reason and から closes it.

私わたしはこの計けい画かくに賛さん成せいです。なぜなら、地ち域いきの雇こ用ようを増ふやせるからです。

I support this plan. The reason is that it can increase local employment.

How to form it

Statement。なぜなら、 + plain form + からだ／からです

A noun or な-adjective keeps だ: 必ひつ要ようだからです. なぜならば and からである are stiffer, for writing.

Before it: A full sentence: your opinion, decision or claim.
After it: The reason, closed with からだ, からです or からである.
Tone: Logical and a little stiff. You are building an argument, not chatting.
Where you'll meet it: Essays, exam answers, presentations, speeches, debates. In a school essay it is the standard way to back up 〜と思おもいます.

In use

子こどもにはスマホを持もたせないほうがいいと思おもいます。なぜなら、勉べん強きょうの時じ間かんが減へるからです。

I think it is better not to give children smartphones. The reason is that they will spend less time studying.

この本ほんは初しょ級きゅう者しゃには勧すすめません。なぜなら、専せん門もん用よう語ごの説せつ明めいがほとんどないからです。

I do not recommend this book for beginners. The reason is that it provides almost no explanation of technical terms.

この制せい度どは見み直なおす必ひつ要ようがある。なぜならば、現げん在ざいの規き定ていでは利り用ようできない人ひとが多おおいからである。

This system needs to be reviewed. The reason is that many people are unable to use it under the current rules.

The stiffest version, for reports and academic writing.

Two things to know

It doesn't work like English "because"

English "because" can start a sentence and needs nothing at the end. なぜなら only comes after the statement it explains, and the reason still has to be closed at the end, nearly always with から.

Not said: なぜなら雨あめが降ふっているから、行いきません。

(Because it is raining, I won't go.)

With the reason first, から alone does the job: 雨あめが降ふっているから、行いきません.

Not said: 行いきません。なぜなら、雨あめが降ふっています。

(I won't go. The reason is that it is raining.)

The reason is left open. Say 降ふっているからです.

In conversation it sounds like a speech

In everyday talk people just add the reason with から.

Sounds odd: 今日きょうは行いけない。なぜなら、バイトがあるからだ。

I can't go today. The reason is that I have a shift at work.

To a friend: 今日きょうは行いけない。バイトがあるから。

A

どうして遅おくれたんですか。

Why were you late?

B

電でん車しゃが止とまったからです。

Because the train stopped.

An answer to どうして doesn't open with なぜなら either. It just ends in からです.

Close neighbours

からN5

The everyday "because". The reason comes first, inside the same sentence.

雨あめが降ふるから、傘かさを持もっていきます。

It is going to rain, so I will take an umbrella.

なぜかというと・どうしてかというとN3

The spoken cousin: "and why? Well…". Softer, and common when you are explaining something out loud.

私わたしは朝あさ早はやく会かい社しゃに行いきます。なぜかというと、電でん車しゃが空すいているからです。

I go to the office early in the morning. Why? Because the trains are empty.

Check yourself

1Which ending?

私わたしは反はん対たいです。なぜなら、値ね段だんが高たかい（　　）。

Choose an answer to see why.

2"It's cold, so I'm staying home."

Choose an answer to see why.

3You are texting a friend. Which sounds natural?

Choose an answer to see why.

More sentences

今いまは契けい約やくを更こう新しんしないほうがよい。なぜなら、来らい月げつから条じょう件けんが変かわるからだ。

It would be better not to renew the contract now. The reason is that the terms will change next month.

会かい議ぎはオンラインで行おこないます。なぜなら、参さん加か者しゃの半はん数すうが海かい外がいにいるからです。

The meeting will be held online. The reason is that half of the participants are overseas.

発はっ表ぴょうでは最さい初しょに結けつ論ろんを述のべます。なぜなら、そのほうが聞きき手てに要よう点てんが伝つたわりやすいからです。

In a presentation, I state the conclusion first. The reason is that this makes it easier for the audience to grasp the main point.