Any planned or unplanned alteration of a state, configuration, quantity etc. in an organism, situation or process. Change may extend over a period of time and it may be a very complex phenomenon. It is a universal characteristic, an invariant, within systems.
Open your arms to change, but don't let go of your values.
It's not the strongest of the species that survive, nor the most intelligent, but the ones most responsive to change. (Charles Darwin).