41-XX Approximations and expansions, {For all approximation theory in the complex domain, See {30Exx} {30E05 and 30E10}; for all trigonometric approximation and interpolation, See {42Axx} {42A10 and 42A15}; for numerical approximation, See 65Dxx} ( 1 Dok.)

• 41-00 General reference works (handbooks, dictionaries, bibliographies, etc.) ( 0 Dok.)
• 41-01 Instructional exposition (textbooks, tutorial papers, etc.) ( 0 Dok.)
• 41-02 Research exposition (monographs, survey articles) ( 0 Dok.)
• 41-03 Historical (must be assigned at least one classification number from Section 01) ( 0 Dok.)
• 41-04 Explicit machine computation and programs (not the theory of computation or programming) ( 0 Dok.)
• 41-06 Proceedings, conferences, collections, etc. ( 0 Dok.)
• 41A05 Interpolation, See also {42A15 and 65D05} ( 0 Dok.)
• 41A10 Approximation by polynomials, {For approximation by trigonometric polynomials, See 42A10} ( 0 Dok.)
• 41A15 Spline approximation ( 0 Dok.)
• 41A17 Inequalities in approximation (Bernstein, Jackson, Nikolskiui type inequalities) ( 0 Dok.)
• 41A20 Approximation by rational functions ( 1 Dok.)
• 41A21 Pade approximation ( 0 Dok.)
• 41A25 Rate of convergence, degree of approximation ( 0 Dok.)
• 41A27 Inverse theorems ( 0 Dok.)
• 41A28 Simultaneous approximation ( 0 Dok.)
• 41A29 Approximation with constraints ( 0 Dok.)
• 41A30 Approximation by other special function classes ( 0 Dok.)
• 41A35 Approximation by operators (in particular, by integral operators) ( 0 Dok.)
• 41A36 Approximation by positive operators ( 0 Dok.)
• 41A40 Saturation ( 0 Dok.)
• 41A44 Best constants ( 0 Dok.)
• 41A45 Approximation by arbitrary linear expressions ( 0 Dok.)
• 41A46 Approximation by arbitrary nonlinear expressions; widths and entropy ( 0 Dok.)
• 41A50 Best approximation, Chebyshev systems ( 0 Dok.)
• 41A52 Uniqueness of best approximation ( 0 Dok.)
• 41A55 Approximate quadratures ( 0 Dok.)
• 41A58 Series expansions (e.g. Taylor, Lidstone series, but not Fourier series) ( 0 Dok.)
• 41A60 Asymptotic approximations, asymptotic expansions (steepest descent, etc.), See also {30E15} ( 0 Dok.)
• 41A63 Multidimensional problems (should also be assigned at least one other classification number in this section) ( 0 Dok.)
• 41A65 Abstract approximation theory (approximation in normed linear spaces and other abstract spaces) ( 0 Dok.)
• 41A80 Remainders in approximation formulas ( 0 Dok.)
• 41A99 Miscellaneous topics ( 0 Dok.)