_ included in the symbol: A is included in B- then A is a subset of B or equal to B ... _ is included in the symbol: A includes B-then B is a subset of A or equal to A.

_ True Inclusion: A is really included in the proper subset of B-if B = {1, 2}, then A={ 1} or {2} or an empty set.

Operation symbols: such as plus sign (+), minus sign (-), multiplication sign (× or) and division sign (÷ or/).

Union (∩), intersection (∩), root sign (∩), logarithm (log, lg, ln, lb), ratio (:), absolute value sign ||, differential (d), integral (∩), closed surface (curve