The concentration of particles in a solution; also known as osmolality.

Osmotic pressure due to concentration of those particles that do not penetrate a cell membrane. Compare osmolality, isotonic, hypertonic and hypotonic.

Tonicity is the ability of a solution to cause water movement. It is in reference to hypertonic, hypotonic and isotonic cellular states.

The state of healthy tension or partial contraction of muscle fibers while at rest; tone; tonus.

the elastic tension of living muscles, arteries, etc. that facilitate response to stimuli; "the doctor tested my tonicity"