Symmetry – in the abstract – defines how two things are the same under some transformation. The term symmetry comes from the Greek word meaning 'to measure together.' Geometrically, symmetry means that one shape becomes exactly like another when it is moved in some way: when a turn, flip or slide transformation is performed. This concept can be generalized to describe how two or more things are the same under some transformation. Symmetry can be used to define the level of order within a system. While symmetry defines "sameness" and order, asymmetry defines how things are different.