Functions can be classified based on various criteria such as their nature, behavior, continuity, and injectivity/surjectivity. The main classifications include:
1. Based on the nature of the function: Linear, Quadratic, Polynomial, Rational, Exponential, Logarithmic.
2. Based on the behavior of the function: Even, Odd, Periodic.
3. Based on continuity: Continuous, Discontinuous.
4. Based on injectivity and surjectivity: Injective (One-to-One), Surjective (Onto),Bijective (Both injective and surjective).