Slashes may also be used as a combining character in mathematical formulae. The most important use of this is that combining a slash with a relation negates it, producing e.g. 'not equal' formula_24 as negation of formula_25 or 'not in' formula_26 as negation of formula_27; these slashed relation symbols are always implicitly defined in terms of the non-slashed base symbol. The graphical form of the negation slash is mostly the same as for a division slash, except in some cases where that would look odd; the negation formula_28 of formula_29 (divides) and negation formula_30 of formula_3 (various meanings) customarily both have their negations slashes less steep and in particular shorter than the usual one.