性質
せいしつ · seishitsu · JLPT N3 · noun
nature
🧬 性質 = inborn nature (性) + substance or quality (質)
性 is the nature something is born with, as in 性格 (personality). 質 means quality or substance, as in 品質 (product quality). Put together, they mean the built-in qualities of a person or thing: its nature, properties or disposition.
性 — heart radical 忄 + 生 (life/birth)
性 is a semantic-phonetic compound. The heart radical 忄 supplies the meaning, pointing to inner feelings or innate qualities, while 生 ('birth, life') gives the sound and hints at what one is born with. It originally meant 'inborn nature' and later extended to 'character,' 'gender,' and 'sex.'