weak constitution; frail health
Describes a person who is physically weak, gets sick easily, or has low stamina. Often used in medical or everyday contexts.
He has a weak constitution and often catches colds.
I had a frail constitution as a child, but now I'm healthy.
病弱 is an adjective meaning 'sickly' or 'weakly', often used to describe a person's general state, while 虚弱体質 is a noun specifically referring to a constitutional weakness.
虚弱 is a shorter noun/adjective meaning 'weakness' or 'frailty', but 虚弱体質 emphasizes the inherent physical constitution.
Compound of 虚弱 (weakness, frailty) and 体質 (constitution, physical makeup). The word is a straightforward Sino-Japanese compound.