1. The result of the addition of two or more quantities, with the addition of a negative quantity equivalent to subtraction of the corresponding positive quantity.

2. For two fuzzy sets A and B, with membership functions m_A and m_B, that fuzzy set whose membership function m_A+B satisfies the equation m_A+B(x ) = m_A(x ) + m_B(x ) - [m_A(x ) · m_B(x )] for every element x.