能动性是一个生物学术语，意指能自发且独立地移动。此一名词可以应用在单细胞和多细胞的生命体上头。

在细胞生物学和生医工程中，能动性通常是指细胞随着生物聚合物形成的梯度而有方向性的移动。例子如下：

• 沿着化学梯度的移动（见化学趋向性）
• 沿着刚性梯度的移动（见刚性趋向性）
• 沿着细胞接合位置梯度的移动（见接触趋向性）

In biology, motility is the ability to move spontaneously and actively, consuming energy in the process. Motility is genetically determined (see genetic determinism) but may be affected by environmental factors. For instance, muscles give animals motility but the consumption of hydrogen cyanide (the environmental factor in this case) would adversely affect muscle physiology causing them to stiffen leading to rigor mortis. Most animals are motile but the term applies to unicellular and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in addition to animal locomotion. Motile marine animals are commonly called free-swimming.