The present invention provides a stator and a motor assembly including the same. The stator includes: a stator core disposed outside a rotor core and having an inner surface inclined with respect to a rotation axis of a rotor; a plurality of coil-wound teeth extending from the inner surface of the stator core towards the rotation axis, wherein a coil is wound around each of the plurality of coil-wound teeth; and openings formed by sidewalls of the plurality of coil-wound teeth and the inner surface of the stator core, wherein a cross-sectional area of the openings changes along a direction of the rotation axis.
