N2Grammar

のではないでしょうか

I think ... isn't it?, It might be that..., Don't you agree?

Structure

Verb + の⁽¹⁾ + ではない⁽²⁾（だろう）か

［い］Adjective + の⁽¹⁾ + ではない⁽²⁾（だろう）か

Noun + （なの⁽³⁾）+ ではない⁽²⁾（だろう）か

［な］Adjective + （なの⁽³⁾）+ ではない⁽²⁾（だろう）か

⁽¹⁾ ん
⁽²⁾ じゃない
⁽³⁾ なん

Explanation

のではないだろうか is a lengthy but common grammar pattern used to present a personal opinion or conjecture in a softened, indirect way. It functions like a rhetorical question, often translated as 'I think...', 'It might be...', or '...don't you think?'. It is formed from の, ではない (isn't), だろう (probably), and か (question marker), literally meaning something like, 'Isn't it probably the case that...?'. By phrasing a statement as a gentle question rather than a direct assertion, the speaker sounds more humble and less forceful.

のではないだろうか is attached to the plain form of verbs and い-adjectives. For な-adjectives and nouns, な must be added before it. The more formal でしょう can also be used in place of だろう.

赤ちゃん(あかちゃん)が泣(な)いている。お腹(なか)が空(す)いているのではないだろうか。
The baby is crying. I think she's probably hungry, don't you?
エアコンが効(き)きすぎている。この部屋(へや)は少(すこ)し寒(さむ)いのではないだろうか。
The air conditioning is on too strong. Don't you think this room is a little cold?
佐藤(さとう)さんは最近(さいきん)元気(げんき)がない。何(なに)か大変(たいへん)なことがあったのではないでしょうか。
Sato-san hasn't seemed very energetic lately. I'm thinking something difficult might have happened, wouldn't you agree?
電気(でんき)がつかない。停電(ていでん)なのではないでしょうか。
The lights won't turn on. Could it be a power outage?

This expression is also quite useful for inviting the listener to agree with your assessment, or for gently persuading them toward your point of view.

Examples

あの人(ひと)、新(あたら)しい先生(せんせい)ではないだろうか。

I think that person is the new teacher, isn't she? (don't you agree?)

子供(こども)たちは公園(こうえん)で遊(あそ)んでいるのではないだろうか。

I suspect the children are playing in the park, aren't they? (don't you think?)

このラーメン、見(み)た目(め)はすごいけど、実(じつ)はすごく辛(から)いのではないだろうか。

This ramen looks amazing, but I'll bet it's actually really spicy, don't you think?

この問題(もんだい)の解決(かいけつ)は非常(ひじょう)に困難(こんなん)ではないだろうか。

I think that solving this problem will be extremely difficult, wouldn't you agree?

彼(かれ)は約束(やくそく)を忘(わす)れてしまったのではないだろうか。

I have a feeling he completely forgot about our promise, don't you think?

こちらがお探(さが)しの本(ほん)ではないでしょうか。

I believe this is the book you were looking for, isn't it?

昨日(きのう)の試験(しけん)は、思(おも)っていたより易(やさ)しかったのではないだろうか。

Yesterday's exam was easier than I thought it would be, wouldn't you say?

これなら、子供(こども)でも食(た)べられるのではないだろうか。

Given this, I think even a child could eat it, don't you agree?

電車(でんしゃ)が遅(おく)れている。たぶん事故(じこ)ではないだろうか。

The train is late. I wonder if there was an accident, don't you think?

あのプロジェクトを一人(ひとり)でやったのは、大変(たいへん)だったのではないだろうか。

Doing that project all by himself must have been really tough, don't you think?

彼(かれ)はまだ真実(しんじつ)を知(し)らないのではないだろうか。

I think he still doesn't know the truth, does he? (don't you agree?)

本当(ほんとう)の幸(しあわ)せとは、お金(かね)では買(か)えないものではないだろうか。

True happiness is something that money can't buy, wouldn't you agree?