The psi functions are used to describe the wave functions of quantum systems.

Propositional functions are important in mathematical logic.

Polynomial functions are widely used in mathematics.

Penalty functions are used to enforce constraints in optimization problems.

Truth functions are used in logic to determine the truth value of compound propositions.

The natural functions of the human body are essential for survival.

Membership functions are used in fuzzy logic to define the shape of fuzzy sets.

Orthogonal functions are widely used in signal processing.

The set of orthonormal functions forms a basis for the vector space.

There are many integrable functions in mathematics.