Invariant/ɪnˈveriənt/ Definition 1 of 4Pro Tip 1/2Unchanging Phenomena Use 'invariant' to describe constants in scientific and philosophical contexts. Principles of physics are considered invariants across the universe. Pro Tip 2/2Consistent Characteristics 'Invariant' is not used for temporary or variable conditions. Her interest in biology was an invariant passion throughout her life.