A condition typified by a weakness of voluntary movement (seen as a "letting go" of such movements), or by partial loss of voluntary movement or by impaired movement. When used without qualifiers, it usually refers to the limbs, but it can also be used to describe the muscles of the eyes (ophthalmoparesis), the stomach (gastroparesis), and also the vocal cords (vocal cord paresis).

Neurologists use the term paresis to describe weakness, and plegia to describe paralysis in which all voluntary movement is lost.