Final answer:
A nova is a temporary increase in brightness of a star that occurs in a binary star system with a white dwarf star as one of the components.
Step-by-step explanation:
Nova is a phenomenon that occurs in binary star systems and is caused by a white dwarf star. When the white dwarf accretes enough material from its companion star, a thermonuclear explosion called a nova occurs. This explosion causes a temporary increase in brightness of the star.
For a star or star system to possibly give rise to a nova, it must meet two conditions: it must be a binary star system and it must have a white dwarf star as one of the components. Only then can the accretion of material onto the white dwarf trigger a nova event.