We first review recent measurements of D → μν and Ds → μν, τν from CLEO-c. These decays are used to determine leptonic decay constants fD and fDs which may be compared to modern Lattice QCD (LQCD) calculations. Such cross-checks can provide confidence in Lattice results for B(s) meson decay constants which are needed to fully exploit data used to extract the CKM matrix elements Vub and Vcb. We also comment briefly on the outlook for further progress at BESIII.
Charmed and light pseudoscalar meson decay constants from four-flavor lattice QCD with physical light quarks