a hollow, flexible structure resembling a bag or pouch 袋 a fountain pen with an ink sac. 一枝有墨水袋的自来水笔。 ■a cavity enclosed by a membrane within a living organism, containing air, liquid, or solid structures 囊 ■the distended membrane surrounding a hernia, cyst, or tumour (包住疝、囊肿或肿瘤的)肿胀膜
派生 sac-like adjective 语源
mid 18th cent. (as a term in biology): from French sac or Latin saccus 'sack, bag'