Tonus is the Latin equivalent of the English word tone. It is especially used to refer to: Muscle tone, the continuous and passive partial contraction of the muscles Arterial tone, the continuous and passive partial contraction of the arterioles Tonicity, the ability of a solution to cause water movement The Pythagorean interval of 9/8 A brand of fruit juice produced by the Lebedyansky division of PepsiCo in Russia