硬い, 固い, and 堅い: tendencies among three かたい spellings
Compare common uses of 硬い for resistance to deformation, 固い for a set or fixed state, and 堅い for robustness or reliability. Since their usage overlaps, treat these as tendencies rather than absolute divisions.
硬い: resistant to bending or deformation
硬い is common for bread, metal, frozen ground, and other materials that resist pressure or bending. このパンは一日置いたら硬くなりました。 and 凍った土が硬くてスコップが入りません。 are representative examples.
It can extend to language in 硬い表現, describing wording that feels formal and inflexible. Do not restrict 硬い to physical objects; instead, follow the central image of something that is not flexible or yielding.
固い: set, fixed, or difficult to loosen
固い is common when a substance has solidified or a state is firmly fixed. この木の実は殻が固いです。 and ひもを固く結びました。 describe a shell and a knot that do not easily give way or come loose.
It also appears in abstract expressions such as 緊張で表情が固くなりました。 and 固い決意. The focus is a facial expression, attitude, or resolve that has become fixed and does not readily soften or change.
堅い: robust, dependable, or secure
堅い is common for robust structures and for dependable people or judgments. この箱は堅い木で作られています。 and 彼は口が堅いので秘密を守ります。 describe sturdy wood and a person trusted to keep a secret.
Expressions such as 勝利は堅い and 堅い仕事 present a result as highly likely or a livelihood as stable. Dictionaries and editorial styles may overlap in their use of 硬い, 固い, and 堅い, and writers may choose hiragana かたい. Learn representative combinations without declaring another spelling wrong in isolation.
Quick check: Following the representative tendencies in this guide, what does each phrase emphasize in 硬いパン, 固い決意, and 勝利は堅い?
Show the answer and why
硬いパン emphasizes material hardness, 固い決意 emphasizes resolve that will not change easily, and 勝利は堅い presents victory as highly certain. Actual spelling can overlap, so these examples are tendencies rather than an absolute rule.