hypo-

CIDE DICTIONARY

hypo-,  [Gr. under, beneath; akin to L. sub. See Sub-.].

•  A prefix signifying a less quantity, or a low state or degree, of that denoted by the word with which it is joined, or position under or beneath.  [1913 Webster]
•  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.  [1913 Webster]

OXFORD DICTIONARY

hypo-, prefix (before a vowel or h usu. hyp-)
1 under (hypodermic).
2 below normal (hypoxia).
3 slightly (hypomania).
4 Chem. containing an element combined in low valence (hypochlorous).

Etymology

Gk f. hupo under