gill science definition

1. The organ that enables most aquatic animals to take dissolved oxygen from the water. It consists of a series of membranes that have many small blood vessels. Oxygen passes into the bloodstream and carbon dioxide passes out of it as water flows across the membranes.
2. One of the thin strips of tissue on the underside of the cap of many species of basidiomycete fungi. Gills produce the spore-bearing structures known as basidia.

gill

Fish breathe by swallowing water, and passing it through gill slits on each side of their head. Blood-filled filaments on the gills extract oxygen from the water as it flows through.