ΛCDM or Lamda-CDM is an abbreviation for Lambda-Cold Dark Matter. It represents the current concordance model of cosmology that explains cosmic microwave background observations, as well as large scale structure observations and supernovae observations of the accelerating expansion of the universe.

Λ (Lambda) stands for the cosmological constant which is a dark energy term that allows for the current accelerating expansion of the universe. Currently, approximately 70% of the energy density of the present universe is in this form.

Cold dark matter is the model where the dark matter is explained as being non-baryonic and collisionless. This component makes up 26% of the energy density of the present universe. The remaining 4% is all of the matter and energy that makes up the atoms and photons that are the building blocks of planets, stars, and gas clouds in the universe.