I want to say "It is necessary for you to go home early.", which is the natural way to say it?

A: あなたがすぐ帰ることは必要だ。

B: あなたがすぐ帰る必要はある。

I am looking for a natural pattern to convey requirement that someone else must do. Other examples are as follows:

 A: 進学するために、あなたが150時間の勉強をすることが必要だ。

 B: 進学するために、あなたが150時間の勉強をする必要はある。

2 Answers 2


?? あなたがすぐ帰ることは必要だ。
○ あなたが会員であることが必要だ。

Construction like 「(subject + verb) ことが必要だ」 is highly unnatural, except when the verb is copula だ/である. In addition, ~は必要だ makes all that comes before は into topic (i.e. background) so that effectively put the focus on 必要だ. It'd mean "It is NECESSARY (as opposed to optional, unrequired etc.)"


あなたがすぐ帰る必要はある。 It IS necessary that you go home immediately.
× あなたがすぐ帰る必要がある。 (it makes no sense with no emphasis)
あなたがすぐ帰る必要がある。 It is necessary that you GO HOME immediately.
あなたがすぐ帰る必要がある。 It is necessary for YOU to go home immediately. (note that the subject has changed)
あなたはすぐ帰る必要がある。 It is necessary for you to go home immediately.

As for the second pair, Japanese prefers leaving subject in first clause rather than in main clause:

A': あなたが進学するためには、150時間の勉強が必要だ。
B': あなたが進学するためには、150時間勉強する必要がある。

(modified wordings for naturalness)

Or you can change it into a single-clause sentence:



B, although I would replace "が" and "は".


As for your two other examples, I would also rephrase them so that "あなた" becomes the subject.

  • if i say 'すぐかえることがなければなりませんです' will it be grammatically correct? Thanks :) btw #oot *it's very strange that i cannot seem to mention your name properly, it will always automatically abbreviated to kilumanga and removed the @'
    – Alice28
    Commented May 27, 2016 at 9:06
  • 1
    @Alice28 "ません" is not followed by "です" and "かえることがなければ" means something different; something along the lines of "if someone (or something) does not go home". It sounds pretty vague and weird. But you could say "かえらなければなりません". Btw, even if you don't put the at-mark annotation, I will get a notification, since I am the author of this post. Commented May 27, 2016 at 9:48
  • 1
    Ah i see :D Thank you very much for clearing that up :) so すぐかえらなければなりません is okay?
    – Alice28
    Commented May 27, 2016 at 9:51

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