Webster's Revised Unabridged Dictionary · 1913

Hypo-

Hypo-

[Greek {not transcribed} under, beneath; akin to Latin sub. See Sub-.]

1.
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.
2.
(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.

Hypo , noun

Hypochondria. [Colloquial]

Hypo , noun

[Abbrev. from hyposulphite.]

(Photography) Sodium hyposulphite, or thiosulphate, a solution of which is used as a bath to wash out the unchanged silver salts in a picture. [Colloquial]