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硬{かた}い, 堅{かた}い, and 固{かた}い all have very similar meaning and can be generally translated to English as "hard, tough, solid, stiff". Yet it seems that different kanji are used in different situations. From what I could gather, the differences might be:

  • 硬い is used especially for stone or metal (e.g. 硬い石),

  • 堅い is used for wood (e.g. 堅い材木); it also means stiff, formal (e.g. 堅い言葉),

  • 固い means stiff, not flexible (e.g. 固いカラー); also means stubborn, unyielding (e.g. 固い約束).

Am I right? There seem to be spellings used for wood, stone or metal, what about other substances? Are there situations where those kanji are interchangable or maybe the word is written using hiragana as かたい?

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up vote 3 down vote accepted

This has an entry in the 異字同訓漢字の使い分け例. My answer will basically just be a quick translation and notes on that entry.


堅 is for stuff that's strong or certain. Stiff, as you say, might be a good word also. Something that is in itself firm and hard, as in wood, or certain, like passing a test.

固 is for something that has a sense of being strongly interconnected (結びつき) or unwavering (揺るがない). So like 団結が固い, strongly united, or 固い決意, where someone might be said to have firm resolve. Note this is the kanji in words like 頑固 as well (stubborn).

硬い is "hard" in the most basic sense of "the opposite of soft." It has literal "hard" meaning, like a rock, but refers metaphorically to being unresponsive to outside stimuli in the way that a hard object resists outside forces, as in for example your facial expression. The entry mentions some athlete who freezes up from nervousness. 硬い表現 refers to an expression that is "hard" in the sense that its meaning is precise and clear: there's no wiggle room for interpretation or emotion. In that sense the word/expression is "hard."

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Thanks for that. I start to think that this is one of those words where you can't come up with hard and fast rules and usage of different kanji is a bit blurry and overlaps. I just found 固いベッド in a short story I'm reading which goes a bit against what is given above. Language is an interesting topic to study... – Szymon Apr 21 '14 at 4:04
Ultimately I think it just comes down to that sort of native intuition, similar to how Japanese people often have very poor usage of the/a. Just need to develop that cultural and linguistic intuition for what sorts of items fit into which categories. Nevertheless I'd certainly be happy if a native posted a more nuanced discussion of different examples. – ssb Apr 21 '14 at 4:19

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