Mass in special relativityThe word "mass" has two meanings in special relativity: invariant mass (also called rest mass) is an invariant quantity which is the same for all observers in all reference frames, while the relativistic mass is dependent on the velocity of the observer. According to the concept of mass–energy equivalence, invariant mass is equivalent to rest energy, while relativistic mass is equivalent to relativistic energy (also called total energy).
Conservation of massIn physics and chemistry, the law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as the system's mass cannot change, so the quantity can neither be added nor be removed. Therefore, the quantity of mass is conserved over time. The law implies that mass can neither be created nor destroyed, although it may be rearranged in space, or the entities associated with it may be changed in form.
CodependencyIn psychology, codependency is a theory that attempts to explain imbalanced relationships where one person enables another person's self-destructive behavior such as addiction, poor mental health, immaturity, irresponsibility, or under-achievement. Definitions of codependency vary, but typically include high self-sacrifice, a focus on others' needs, suppression of one's own emotions, and attempts to control or fix other people's problems.
