ISO 31-11 was the part of international standard ISO 31 that defines mathematical signs and symbols for use in physical sciences and technology. It was superseded in 2009 by ISO 80000-2.
Its definitions include the following:
Read more about ISO 31-11: Mathematical Logic, Sets, Miscellaneous Signs and Symbols, Operations, Functions, Exponential and Logarithmic Functions, Circular and Hyperbolic Functions, Complex Numbers, Matrices, Coordinate Systems, Vectors and Tensors, Special Functions