  A measurement of jet substructure observables is presented using
$\mathrm{t\overline{t}}$ events in the lepton+jets channel from proton-proton
collisions at $\sqrt{s} =$ 13 TeV recorded by the CMS experiment at the LHC,
corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Multiple jet
substructure observables are measured for jets identified as bottom,
light-quark, and gluon jets, as well as for inclusive jets (no flavor
information). The results are unfolded to the particle level and compared to
next-to-leading-order predictions from POWHEG interfaced with the parton shower
generators PYTHIA 8 and HERWIG 7, as well as from SHERPA 2 and DIRE 2. A value
of the strong coupling at the Z boson mass, $\alpha_S(m_\mathrm{Z}) = $ 0.115
$^{+0.015}_{-0.013}$, is extracted from the substructure data at leading-order
plus leading-log accuracy.
