i-adjective
Describes a person or body that is physically weak, delicate, or prone to illness. Often used for children or people with a frail constitution.
彼は子供の頃ひ弱くて、よく病気になった。
He was weak as a child and often got sick.
ひ弱い体を鍛えるためにジムに通い始めた。
I started going to the gym to strengthen my frail body.