what is the difference between oxidation state and oxidation number in redox reactions.

Oxidation state and oxidation numbers both are the terms that are often used interchangeably.In order to keep track of electron transfer during the formation of covalent compounds,a more practical method of using the concept of oxidation number has been developed,in which it is always assumed that there is complete transfer of electron from a less electronegative atom to a more electronegative atom.
Oxidation number – It denotes the oxidation state of an element in a compound which is ascertained according to a set of rules which are formulated on the basis that electron in a covalent bond belongs entirely to more electronegative element.
According to rules metallic elements have positive and non-metallic elements have positive or negative oxidation sates.Transition element shows several oxidation states.
Oxidation state – Oxidation number denotes the oxidation state of an element in a compound.For ex- oxidation state of C in CO2 ic +4 which is also its oxidation number.
According to Stock notation oxidation number is expressed by putting a Roman numeral reperesenting the oxidation number in parenthesis after the symbol of the metal in molecular formula.For ex- Sn(II)Cl2,Hg(II)Cl2.