堅; 硬; 固い
かたい · katai · JLPT N4 · i-adj
hard
🪨🧱 katai = kata (a fixed form) + i: what holds its form is hard
Japanese kata (型/形) means a set form or mould, as in karate kata. Katai shares that root: something that keeps its form and does not give way. The kanji 固, 硬 and 堅 all write this same word for firm, hard and solid.
硬 — stone 石 + 更 (gēng, phonetic)
硬 is a semantic-phonetic compound. The left side 石 'stone' gives the meaning—stones are hard—while the right side 更 originally suggested the pronunciation. From the literal sense of stone-hardness, 硬 extended to mean firm, stiff, or stubborn in both physical and figurative uses.