1. (Science: prefix) a prefix signifying a less quantity, deficient, below normal or a low state or degree, of that denoted by the word with which it is joined, or position under or beneath. For example, hypocalcaemia is olow calcium in the blood.
2. (Science: chemistry) a prefix denoting that the element to the name of which it is prefixed enters with a low valence, or in a low state of oxidization, usually the lowest, into the compounds indicated; as, hyposulphurous acid. Used to denote the lowest, or least rich in oxygen, of a series of chemical compounds.