nucleoside diphosphate

nu·cle·o·side di·phos·phate (NDP),

the pyrophosphoric ester of a nucleoside, that is, a nucleoside in which the H of one of the ribose hydroxyls (usually the 5') is replaced by a pyrophosphoric (diphosphoric) radical, for example, adenosine 5'-diphosphate. Compare: nucleoside bisphosphate.