The basic unit into which the lithosphere is broken is a plate.
According to the plate tectonics the Earth's lithosphere is broken into many pieces that move slowly over the asthenosphere (the soft, flexible layer of the mantle on which the tectonic plates move and float). These tectonic plates move at a rate of centimeters per year. Lithosphere is the chunk of crust and upper mantle that moves the Earth's surface. Therefore; one would say the tectonic plates, are the blocks, chunk or pieces of lithosphere that move around on the top of the asthenosphere.