ABSTRACT
Orthogonality of a pair of binary groupoids, left quasigroups and quasigroups is studied from some points of view. Necessary and sufficient conditions of orthogonality of a finite quasigroup and its parastrophe (conjugate quasigroup in other terminology), including ones in the language of quasi-identities, are given. A new concept of gisotopy, which generalizes the concept of isotopy, is defined. There is information on quasigroups with self-orthogonal conjugates. In general we follow the article [643].
