\Hy"dro-\, Hydr- \Hy"dr-\
1. A combining form from Gr. ?, ?, water (see {Hydra}).

2. (Chem.) A combining form of hydrogen, indicating hydrogen
   as an ingredient, as hydrochloric; or a reduction product
   obtained by hydrogen, as hydroquinone.

\Hy"dro\, n.
A hydro-a["e]roplane.