Invisible Matter which can't be observed or measured directly.
A type of matter in astronomy and cosmology hypothesized to account for effects that appear to be the result of mass where no such mass can be seen.
The total mass–energy of the known universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy.
Thus, dark matter is estimated to constitute 84.5% of the total matter in the universe, while dark energy plus dark matter constitute 95.1% of the total content of the universe.