  We discuss properties and examples of r-mode (large scale Rossby wave)
oscillations in rotating stars. Motions are nearly toroidal but affected weakly
by buoyancy. R modes seem to be excited mechanically in most cases, and
ubiquitous in various types of rotating stars;e.g., fast rotating $\gamma$ Dor
stars, spotted stars, eclipsing binary stars, Be stars, and accreting white
dwarfs. In the Fourier spectrum of a star, even (i.e., symmetric to the
equator) r modes of azimuthal order $m$ appear as a group of frequencies just
below $m$ times the rotation frequency. From this property, a rotation
frequency can be determined if r modes are detected. We discuss r modes in
KIC8462852 (Boyajian's star), KIC9117875 (Am star), KIC6128830 (HgMn star), and
the accreting white dwarf in the dwarf nova GW Lib.
