  As quantum computers mature, the applicability in practice becomes more
important. Many uses of quantum computers will be hybrid, with classical
computers still playing an important role in operating and using the quantum
computer. The term hybrid is however diffuse and multi-interpretable. In this
work we define two classes of hybrid quantum-classical computing: vertical and
horizontal. The first is application-agnostic and concerns using quantum
computers. The second is application-specific and concerns running an
algorithm. For both, we give a further subdivision in different types of hybrid
quantum-classical computing and we coin terms for them.
