What is electronegativity?

What is electronegativity ? What are various methods used to determine electronegativity ? Explain.

Electronegativity : The electronegativity of an element is defined as the relative tendency of its atom to attract electrons towards itself when it is bounded to the atom of another elements.
Various methods to calculate electronegativity :
Milliken scale : According to Milliken, the electronegativity of an element is average value of its ionization energy and electron affinity.
Pauling scale : Pauling scale is based on bond energies. The electronegativity hydrogen is assumed as 2.20. Electronegativity of other elements are calculated with respect to hydrogen.