Identity function

Constant function

Polynomial function

One – one function

onto function

y = f(x) = x for each x ∈ R

y = f(x) = c for each x ∈ R

y = f (x) = a₀ + a₁x + a₂x² + ...+ an xⁿ, where n is a non-negative integer

f: A→B , if distinct elements of A have distinct images in B

f: A→B ,if the range of f is equal to the co-domain of f