sickly, prone to illness
彼は病弱なので心配だ。
I'm worried about him because he's frail.
私の弟はずっと病弱です。
My younger brother has always been frail.
彼女は子供のころ病弱だったらしい。
Apparently, she was sickly as a child.
母は病弱にもかかわらず、いつもすごく明るい。
Despite being in poor health, my mother is always very cheerful.
彼女は生まれた時から病弱だった。
She had been frail since birth.