non-logical connective/mekso operator - of arity only 1 xor 2: set (absolute) complement, or set exclusion (relative complement). Unary: X2 ^C; binary: X1\setminusX.
Each input must be a set or similar. The definition of the binary case expands to "the set of exactly those elements which are in X1 but not in X2". This word and operator has ordered input: 'X1 kei'i X2' is not generally equivalent to 'X2 kei'i X1'; in other words, the operator is not commutative. If unary (meaning that X1 is not explicitly specified in a hypothetical expression "X1\setminusX"), then X1 is taken to be some universal set O in/of the discourse (of which all other mentioned or relevantly formable sets are subsets, at the least); in this latter case, the word operates as the set (absolute) complement of the explicitly mentioned set here designated as X2 for clarity (id est: the output is O\setminusX2=X2^C, where "C" denotes the set absolute complement; in other words, it is the set of all elements which may be under consideration such that they are not elements of the explicitly specified set). When binary with both X1 and X2 explicitly specified, this word/operator is the set relative complement. This word is somewhat analogous to, depending on its arity, logical 'NOT' or 'AND NOT' (just as set intersection is analogous to logical 'AND', set union is analogous to logical '(AND/)OR' and set symmetric difference is analogous to 'XOR'). The preferred description/name in English is "set (theoretic) exclusion". See also: "kleivmu". For reference: https://en.wikipedia.org/wiki/Complement_(set_theory) .