My dictionary defines both 防止 and 予防 as "prevention", with 予防 having the additional definitions of "precaution" and "protection against".

I sort of understand the latter definitions for 予防 as acting to stop something which is happening from getting worse, which explains its use in medicine, but I've also seen 予防 used in the "prevention" sense similar to 防止. For example, from the Tanaka Corpus:

The prevention of forest fires is everyone's responsibility.

This is Fire Prevention Week.

We must take measures to prevent traffic accidents.

Defensive driving can help you avoid accidents.

It is essential to prevent salmonella contamination in hen egg production.

Prevention is much preferable to cure. [sic]

In what situations is it preferable to use 防止 over 予防? What are the nuances that govern the choice of one word over the other?

3 Answers 3


The key to understanding the difference is in the characters, the 予 of 予防 can be seen in the phrase 予め also, meaning "in advance" or "beforehand". While the 止 of 防止 can be seen in the phrase 止める, meaning "to stop something". In other words, 予防 doesn't mean to stop something, it means to do something in advance to try to prevent it as you aware that it might happen, whereas 防止 just means to stop something from happening (prevent it) and doesn't include the "in advance" part.

So, to take your first two examples:

森林火災の防止 means to stop (prevent) forest fires, whereas 火災予防 implies doing something in advance to try to prevent fires from happening as you are aware that they might happen.


Kurosawa explains the difference as:

(再発)防止:prevent the deplorable event from happening again (event having occurred once or more before)

予防:prevent a deplorable event from ever happening (event not yet occurred)

(sorry for posting this as an answer; I can't seem to comment on any of the other entries)

  • 1
    Thanks for the article link. You won't be able to leave comments on other people's questions and answers until you have 50 reputation as an anti-spam measure.
    – Troyen
    Commented Aug 8, 2012 at 23:19
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    This is not an explanation of the difference between 防止 and 予防, but an explanation of the difference between 再発防止 and 予防, which is kind of obvious once you know 再発 means “to happen again.” Commented Aug 9, 2012 at 2:20
  • Sincere apologies that I wasn't clear about the article doesn't explain the difference, only thought it might help to distinguish between the two words (also then reason why I initially wanted to post as a comment, not an answer)
    – softbear
    Commented Aug 9, 2012 at 8:37
  • Uh, it is you who wrote “Kurosawa explains the difference as….” (Not that I would like to blame you, but your comment “I wasn't clear about the article doesn't explain the difference” is just puzzling me.) Commented Aug 9, 2012 at 15:02

My understanding is that 防止 means "prevent something from happening" whereas 予防 means "assuming that something will happen, prevent or lessen in advance the negative impact of it".

  • So do you mean 防止 means "we know that the thing will happen so we have to stop it", and 予防 means "we don't know if it will happen or not (起こるとしたら...), but let's take some action to make sure it doesn't"?
    – istrasci
    Commented Aug 8, 2012 at 14:24

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