硬い・堅い・固い - how are different spellings used?


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?




This has an entry in the
[異字同訓漢字の使い分け例](http://www.bunka.go.jp/kokugo_nihongo/bunkasingi/pdf/ijidoukun_140221.pdf).
My answer will basically just be a quick translation and notes on that entry.

> 【堅い】中身が詰まっていて強い。確かである。  
>  堅い材木。堅い守り。手堅い商売。合格は堅い。口が堅い。堅苦しい。  
>  【固い】結び付きが強い。揺るがない。  
>  団結が固い。固い友情。固い決意。固く信じる。頭が固い。  
>  【硬い】（⇔軟らかい）。外力に強い。こわばっている。  
>  硬い石。硬い殻を割る。硬い表現。表情が硬い。選手が緊張で硬くなっている。

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."




This has an entry in the
[異字同訓漢字の使い分け例](http://www.bunka.go.jp/kokugo_nihongo/bunkasingi/pdf/ijidoukun_140221.pdf).
My answer will basically just be a quick translation and notes on that entry.

> 【堅い】中身が詰まっていて強い。確かである。  
>  堅い材木。堅い守り。手堅い商売。合格は堅い。口が堅い。堅苦しい。  
>  【固い】結び付きが強い。揺るがない。  
>  団結が固い。固い友情。固い決意。固く信じる。頭が固い。  
>  【硬い】（⇔軟らかい）。外力に強い。こわばっている。  
>  硬い石。硬い殻を割る。硬い表現。表情が硬い。選手が緊張で硬くなっている。

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."

