A combinatorial proof establishes the equivalence of different expressions by showing that they count the same object in different ways. Often a bijection between two sets is used to show that the expressions for their two sizes are equal. Alternatively, a double counting argument provides two different expressions for the size of a single set, again showing that the two expressions are equal.

প্রমাণের সমাপ্তিতে
Elementary proof
কম্বিনেটরিক্সের মাধ্যমে প্রমাণ
Statistical proof using data