How can we say that a certain has higher electronegativity?

In Copper & Zinc which is more electronegative?

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. The Pauling scale is the most commonly used. Fluorine (the most electronegativeelement) is assigned a value of 4.0, and values range down to caesium and francium which are the least electronegative at 0.7.
Copper is slightly more electronegative than zinc.The electronegativity of copperis higher than that of zinc. Thus, if you put the two metals next to each other (or if you connect them by a wire), some electrons will move from the zinc to the copper.