The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parametrization of the Big Bangcosmological model in which the universe contains a cosmological constant, denoted by Lambda (GreekΛ), associated with dark energy, and cold dark matter (abbreviated CDM). It is frequently referred to as the standard model of Big Bangcosmology, because it is the simplest model that provides a reasonably good account of the following properties of the cosmos: