As far as I can tell, both mean foolish. Checking a dictionary, 愚かしい is defined as 愚かである。ばかげている。which does not help very much. Is there truly no real difference?


2 Answers 2


The two words are similar in meaning and usage. However, two significant differences stand out.

  1. 愚{おろ}かしい is much less commonly used than 愚{おろ}かな.

  2. 愚かしい is virtually never used to refer to people, whereas 愚かな certainly can.

  • "愚かしい" is an old-fashioned phrase. Feb 10, 2017 at 12:08
  • 5
    愚かしい is virtually never used to refer to people -> But... this dictionary gives an example sentence 「何と愚かしい人間だ」... あと「愚かしい男」「愚かしい自分」「愚かしいやつ」などをググるといくらかヒットしますが
    – chocolate
    Feb 11, 2017 at 4:04
  • Google search with quotes for exact matches: 愚かな人 has over 400 times as many results as 愚かしい人. 愚かな男 results in 320 times as many hits. 人間 results in 80 times as many hits. 者 yields 40 times as many results. I consider that to be rare usage.
    – Alex K
    Feb 11, 2017 at 7:59
  • (1) Google search doesn't quantify precisely ... so don't depend on that.
    – virmaior
    Jun 29, 2018 at 16:08
  • (2) similar in meaning and usage doesn't make any sense when one is much less commonly used.
    – virmaior
    Jun 29, 2018 at 16:11

愚か(だ) describes the quality of "absent of wiseness", while 愚かしい, as with many i-adjectives that end in -しい, indicates a kind of mental perception such as sense, emotion or impression. In this sense, 愚かしい is actually telling "felt unwise" or "as if the unwise do", which is interestingly close to English approach to say foolish that is fool + -ish.

Thus you can say these two has slightly different connotation when both are usable:

(emphasizes how nonsense of (people to do) wars)

(emphasizes how (people doing) wars look irrational)

And it's not totally impossible to find some examples only either one sounds valid:

○ 愚かな人間には理解できない foolish humans will not understand
× 愚かしい人間には理解できない

The latter is unacceptable because 愚かしい does not imply inherent, permanent character of foolishness.

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