dark energy

This term is a specialized scientific concept used primarily in cosmology and astrophysics. It carries a neutral, technical connotation, though the word "dark" here does not refer to a lack of light, but rather to the fact that the energy is invisible and its nature remains unknown to science.

As a mass noun representing a theoretical physical property of the vacuum of space, it is treated as uncountable. It does not have a plural form and is typically used without an indefinite article (e.g., "dark energy is" rather than "a dark energy is").