Although all birds have feathers and all birds have wings, some birds do not fly  For example, penguins and ostriches use their wings to move in a different way from other birds  Penguins use their wings only to swim under water at high speeds
Ostriches use their wings only to run with the wind by lifting them as if they were sails
Sailing ships move in a different way from steamships. Both sailing ships and steamships navigate over water, but only sailing ships use sails to move over the surface.