In The Empire Strikes Back, the character Yoda describes the force as an all-pervading energy field.
Irvin Kershner, director, The Empire Strikes Back, 20th-century Fox, 1980, 1:10:00-1:10:56
YODA: For my ally is the Force. And a powerful ally it is. Life creates it, makes it grow. Its energy surrounds us and binds us. Luminous beings are we, not this crude matter. You must feel the Force around you, here, between you, me, the tree, the rock, everywhere, yes, even between the land, and the ship.