Even functionf(−x) = f(x) for every x in the domain. Its graph is symmetric about the y-axis, for example f(x) = x².
Odd functionf(−x) = −f(x) for every x in the domain. Its graph is symmetric about the origin (0, 0), for example f(x) = x³.
Neitherif neither condition holds for all x in the domain.
The domain must be symmetric about zeroif x belongs to the domain, then −x must also belong to it. Otherwise the function cannot be even or odd.