Hypo \Hy"po\, n.
   Hypochondria. [Colloq.]
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Hypo \Hy"po\, n. [Abbrev. from hyposulphite.] (Photog.)
   Sodium hyposulphite, or thiosulphate, a solution of which is
   used as a bath to wash out the unchanged silver salts in a
   picture. [Colloq.]
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Hypo- \Hy"po-\ [Gr. ? under, beneath; akin to L. 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.
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   2. (Chem.) 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]