All built-in special functions begin with a capital letter to differentiate from variables. Some special functions are listed as follows: Orthogonal Polynomials Gamma and Related Functions Zeta and Related Functions Exponential Integral and Related Functions Error Function and Related Functions Bessel and Related Functions Legendre and Related Functions Confluent Hypergeometric Functions Hypergeometric Functions and Generalizations   Orthogonal Polynomials Top of Page   Gamma and Related Functions Top of Page   Zeta and Related Functions Top of Page   Exponential Integral and Related Functions Top of Page   Error Function and Related Functions Top of Page   Bessel and Related Functions Top of Page   Legendre and Related Functions Top of Page   Confluent Hypergeometric Functions Top of Page   Hypergeometric Functions and Generalizations Top of Page