hypertonicity

This term is primarily used in specialized medical and scientific registers. In a clinical neurological context, it describes a pathological state of muscle rigidity, often associated with upper motor neuron lesions. It is distinct from normal muscle tone, implying a dysfunction that restricts movement and increases resistance to passive stretching.

In a biochemical or physiological context, the term refers to osmotic pressure. A hypertonic solution possesses a higher concentration of solutes compared to another solution, creating an osmotic gradient that draws water out of cells. This distinction is critical in pharmacology and fluid therapy to avoid cellular dehydration or crenation.