Bursa

Part of speech: noun

Pronunciation: /ˈbɜːsə/

Definitions

1. A sac filled with fluid that lessens friction and prevents wear between bones and surrounding soft tissues in the body
2. A small pouch or cavity containing synovial fluid that minimizes resistance during the movement of joints and muscles
3. A fluid-filled sac that reduces friction and shields soft tissues from wear as bones move against them

Etymology: The anatomical "bursa" is a word that began as an ordinary object: a purse. Its ancestor is the Ancient Greek "búrsa", which meant a hide or leather, the skin of an animal, and from that sense came the idea of a leather bag. Medieval Latin then used "bursa" for a purse, and English borrowed the Latin form for the small fluid-filled sacs that cushion joints, presumably because each one looks like a little sealed pouch tucked between bone and tissue. The same Greek root lies behind two familiar English words. "Purse" and "bourse" are doublets of "bursa": all three reach English along different routes from the same ancestor, so a financial exchange called a "bourse" and a joint cushion called a "bursa" share a grandparent that once meant nothing more than a leather bag.