In mathematical logic, quantifiers are formal counterparts of natural-language adjectives like all, some, most, few, etc. which indicate the number of objects satisfying a given property. More precisely, a quantifier is an operator that specifies how many individuals in the domain of discourse satisfy an open formula. For instance, the universal quantifier in the first-order formula expresses that all numbers in the domain are non-negative; this formula is true for the natural numbers domain, but false for the integer domain. On the other hand, the existential quantifier in the formula expresses that some numbers in the domain satisfy the given quadratic equation; indeed, both 2 and 3 do.