  Cataclysmic variables are binary stars in which a relatively normal star is
transferring mass to its compact companion. This interaction gives rise to a
rich range of behaviour, of which the most noticeable are the outbursts that
give the class its name. Novae belong to the class, as do the less well known
dwarf novae and magnetic systems. Novae draw their energy from nuclear
reactions, while dwarf novae rely on gravity to power their smaller eruptions.
All the different classes of cataclysmic variable can be accommodated within a
single framework and this article will describe the framework, review the
properties of the main types of system and discuss models of the outbursts and
of the long-term evolution.
