passive transport

This term is a technical biological descriptor used primarily in academic and scientific registers. It describes a spontaneous process driven by the concentration gradient, contrasting sharply with active transport, which requires ATP or other energy sources to move substances against a gradient.

In a pedagogical context, it is often subdivided into specific mechanisms such as simple diffusion, facilitated diffusion, and osmosis. Because it refers to a biological process or mechanism, it is treated as an uncountable concept in scientific discourse.