noun
water absorbency; water absorption capacity
Technical and everyday term for the ability of a material to absorb water. Often used in product descriptions for towels, paper, soil, etc.
このタオルは吸水性が高い。
This towel has high water absorbency.
吸水性に優れた紙おむつを開発した。
We developed a disposable diaper with excellent water absorption capacity.
吸水率 is the water absorption rate or percentage, a measurable value, whereas 吸水性 is the general property or quality of being absorbent.
Compound of 吸水 (kyūsui, 'water absorption') + 性 (-sei, '-ness, property'). The reading is standard on'yomi.