The quantity of the combining power of an atom, expressed in hydrogenunits; the number of hydrogen atoms can combine with, or be exchanged for; valency.
A Boolean operation that is TRUE when both input variables are TRUE or both input variables are FALSE, but otherwise FALSE; the XNOR function.
A number in intersection theory. A positive-dimensional variety sometimes behaves formally as if it were a finite number of points; this number is its equivalence.