  We present multi-band ultraviolet and optical light curves, as well as
visual-wavelength and near-infrared spectroscopy of the Type II linear (IIL)
supernova (SN) 2013by. We show that SN 2013by and other SNe IIL in the
literature, after their linear decline phase that start after maximum, have a
sharp light curve decline similar to that seen in Type II plateau (IIP)
supernovae. This light curve feature has rarely been observed in other SNe IIL
due to their relative rarity and the intrinsic faintness of this particular
phase of the light curve. We suggest that the presence of this drop could be
used as a physical parameter to distinguish between subclasses of SNe II,
rather than their light curve decline rate shortly after peak. Close inspection
of the spectra of SN 2013by indicate asymmetric line profiles and signatures of
high-velocity hydrogen. Late (less than 90 days after explosion) near-infrared
spectra of SN 2013by exhibit oxygen lines, indicating significant mixing within
the ejecta. From the late-time light curve, we estimate that 0.029 solar mass
of 56Ni was synthesized during the explosion. It is also shown that the V -band
light curve slope is responsible for part of the scatter in the luminosity (V
magnitude 50 days after explosion) vs. 56Ni relation. Our observations of SN
2013by and other SNe IIL through the onset of the nebular phase indicate that
their progenitors are similar to those of SNe IIP.
