硬い

1. Origins, structure, and basic meaning

• Structure: 硬い is read as かたい and is an i-adjective for bread, ground, or another material that is physically hard, stiff, or resistant to pressure.
• Basic usage: Use パンが硬くなる for becoming hard and 土が硬い for a current physical condition.

2. Common pitfalls and similar expressions

• Inflection
  • The adverbial form is 硬く, as in 硬くなる, and the past form is 硬かった.
• Other spellings of かたい
  • 硬い suits physical hardness; 固い often concerns firmness or fixity and 堅い solidity or reliability, though context governs the spelling.