健全 (jiàn quán) as an adjective means 'sound, robust, well-developed', often used for systems, institutions, or overall health. Compare with 完善 (wán shàn), which focuses on completeness/perfection, and 强壮 (qiáng zhuàng)/健壮 (jiàn zhuàng), which refer specifically to physical strength. As a verb, it means 'to perfect, strengthen, improve' (e.g., a system or law).