n.1. the absence of variation or motion, as applied, for example, to genetics (invariance in characteristics), personality (few emotional or mood changes), or body position (absence of body sway). 2. in developmental psychology, the degree to which a person maintains the same rank order with respect to a particular characteristic (e.g., intelligence test performance) over time in comparison with peers. 3. the property of a system, either open or closed, that regulates its internal environment and tends to maintain a constant condition. 4.
see statistical stability.