electron density

This term is a specialized technical expression used primarily in quantum chemistry and physics. It describes a spatial distribution rather than a discrete count of particles, shifting the focus from individual electron orbits to a continuous cloud of probability.

Because it refers to a physical property or a mathematical distribution, it is treated as an uncountable noun. It is almost always used in the singular form, even when referring to multiple different maps or calculations, as the "density" itself is a conceptual property of the system.