39Bxx Functional equations and inequalities [See also 30D05]
 39B05 General
 39B12 Iteration theory, iterative and composite equations [See also 26A18, 30D05, 37XX]
 39B22 Equations for real functions [See also 26A51, 26B25]
 39B32 Equations for complex functions [See also 30D05]
 39B42 Matrix and operator equations [See also 47Jxx]
 39B52 Equations for functions with more general domains and/or ranges
 39B55 Orthogonal additivity and other conditional equations

39B62 Functional inequalities, including subadditivity, convexity, etc. [See also 26A51, 26B25, 26Dxx]
(1)
 39B72 Systems of functional equations and inequalities
 39B82 Stability, separation, extension, and related topics [See also 46A22]
 39B99 None of the above, but in this section