Formula nomenclature is a system of names or terms represented by letters and the Greek alphabet assigned to represent equation physical quantities.  Definition symbols vary widely and do not necessaraly represent the information being presented the way an abbreviation does.

A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z