(plee ay) from the French, literally "bent".
A smooth and continuous bending of the knees.
This can be grande-plié, a bend to the deepest position where the heels lift off of the floor. For demi-plié the dancer bends knees until just below the hips, while maintaining classical turn-out at the hip joints, allowing the thighs and knees to be directly above the line of the toes and the heels to stay on the floor.
Plies are usually done in multiples of four at the ballet barre, and are done with accompanying port de bras.