硬貨
こうか · kouka · JLPT N3 · noun
coin
🪙 硬貨 = hard + money: the hard kind, unlike paper notes
硬 means hard or solid and 貨 means goods or currency, as in 通貨 (currency). So 硬貨 is hard money: coins. Banknotes are the opposite, 紙幣, which means paper money.
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.