Abstract: An extension of the conservation equation for angular momentum is established for fluid dynamical purposes. The three components of the angular momentum vector, described in a Cartesian coordinate system, are divided into pairs of “partial angular momentum” terms. Conversation equations are developed for each of these terms. They show that shear stresses (viscous and Ray-nolds stresses) transfer angular momentum between the two terms of a pair, and they provide means nolds to calculate internal transfer of angular momentum between different dynamical regimes of a system. Two such regimes are waves and shear currents and a brief study of the influence of shear stresses on waves and waves’ interactions with currents, is included as an example.