Quantifier: Qualitative term that states the proportion of something in some domain.
In logic the standard quantifiers are "for all" or "for every" or "for each" and "for some" or "there is" or "there are", and in standard logic the two are interdefinable, in that "for all x Ax" is true precisely if "it is not true that for some x not Ax" and "for some x Ax" is true precisely if "it is not true that for all x not Ax".
There are many subtle issues involved in the logic of quantifiers, which was first thought of and created by Frege and, independently, Peirce and Mitchell.
