幼弱 (yòu ruò) is an adjective meaning 'frail' or 'underdeveloped', especially describing young living beings whose bodies or systems are not yet mature or strong. The character 幼 means 'young' or 'juvenile', often referring to early life stages, while 弱 means 'weak' or 'feeble'. Together, they emphasize both youth and physical vulnerability — a combination frequently used in biological, veterinary, or ecological contexts.

This term carries a gentle, somewhat literary tone and is rarely used for adults or abstract concepts. It appears most commonly when discussing newborn animals, hatchlings, or juvenile plants that lack resilience due to immaturity — for example, in wildlife conservation reports or animal husbandry manuals. Unlike the more general 弱 (ruò), 幼弱 specifically implies fragility rooted in developmental stage, not temporary illness or injury.