Baryon:A type of subatomic particle composed of three quarks, such as protons and neutrons, which make up the nuclei of atoms.
Dark Matter:A hypothetical form of matter that cannot be seen directly but accounts for a significant portion of the total mass in the universe, exerting a gravitational influence on visible matter and the large-scale structure of the cosmos.
Closure: The concept in cosmology that the total density of the universe determines its overall geometry and fate, whether it will expand forever, oscillate, or eventually collapse.