D defs.my
Entry 1 sense Webster, 1913

Deuto-

· Deu·to- · IPA
01 A prefix which formerly properly indicated the second in a regular series of compound in the series, and not to its composition, but which …
  1. 1.
    A prefix which formerly properly indicated the second in a regular series of compound in the series, and not to its composition, but which is now generally employed in the same sense as bi- or di-, although little used.(Chem.) Also: bi-, di-