硬質

1. Origins, structure, and basic meaning

• Structure: 硬質 (こうしつ) is a nominal stem describing a hard material or a hard-edged, metallic quality of sound.
• Basic usage: 硬質の素材 modifies a scratch-resistant material, while 硬質な音 attributes a sharp, hard-edged quality to a sound in a corridor.

2. Common pitfalls and similar expressions

• Material hardness and auditory impression
  • 硬質の素材 is a physical property, whereas 硬質な音 is a metaphor for auditory impression. The latter does not mean sound is made of solid material.