N3 — outside your level filter

なぜなら

なぜならnazenaraN3formal

the reason is; because — opens a new sentence explaining the last one

この計画けいかくには反対はんたいです。なぜなら、費用ひようがかかりすぎるからです。

kono keikaku ni wa hantai desu. nazenara, hiyou ga kakarisugiru kara desu.

I'm against this plan. The reason is that it costs too much. neutral

今日きょうは道みちが混こんでいる。なぜなら、近ちかくで工事こうじをしているからだ。

kyou wa michi ga konde iru. nazenara, chikaku de kouji o shite iru kara da.

The roads are congested today. The reason is that there's construction happening nearby. neutral

Same meaning13

because; the reason is

ばかりにall because — one small thing cost far more than it shouldattaches at
だってcasual reason-opener ('cause, X); casual "even N"attaches at
からこそprecisely because — this reason and no other made it happenattaches at
からbecause; so — the speaker's own reasonattaches at
ことだからknowing X as we do — a prediction from someone's known characterattaches at
ものだからbecause — offered as an excuse the speaker could not helpattaches at
もの'cause; but I — a reason fired back at the listenerattaches at
んですit's that…; you see — marks the sentence as an explanationattaches at
なくてnot… and; because (one) doesn'tattaches at
につきowing to N; per N (formal, written)attaches at
のでbecause; since — reason as circumstanceattaches at
せいかperhaps because; maybe it's because — the cause offered only as a guessattaches at
しand what's more — listing reasonsattaches at

All examples3

the reason is; because — introduces the reason for the last sentence

この計画けいかくには反対はんたいです。なぜなら、費用ひようがかかりすぎるからです。
kono keikaku ni wa hantai desu. nazenara, hiyou ga kakarisugiru kara desu.
I'm against this plan. The reason is that it costs too much. neutral
今日きょうは道みちが混こんでいる。なぜなら、近ちかくで工事こうじをしているからだ。
kyou wa michi ga konde iru. nazenara, chikaku de kouji o shite iru kara da.
The roads are congested today. The reason is that there's construction happening nearby. neutral
本ほん研究けんきゅうは重要じゅうようである。なぜなら、これまで十分じゅうぶんな検証けんしょうがなされてこなかったからである。
honkenkyuu wa juuyou de aru. nazenara, koremade juubun na kenshou ga nasarete konakatta kara de aru.
This research is important. The reason is that sufficient verification has not been carried out until now. formal

How it's formed1

All forms1

なぜならばnazenarabaliterary
Keeps the old conditional ば, found in formal writing and speeches.

Notes

Formal essays often close on からである instead of からだ. Casual speech uses だって
instead, since なぜなら has no casual life.