Even: f(-x) = f(x), graph symmetric about y-axis. Examples: $x^2$, cos(x), |x|. Odd: f(-x) = -f(x), graph symmetric about origin. Examples: $x^3$, sin(x), tan(x). The domain must be symmetric about 0. f(x) = 0 is both even and odd. Product of two even or two odd functions is even; product of one even and one odd is odd.