 Principia Mathematica [PM] was written jointly by Alfred North Whitehead and Bertrand Russell over several years, and published in three volumes, which appeared between 1910 and 1913. It presents a system of symbolic logic and then turns to the foundations of mathematics to carry out the logicist project of defining mathematical notions in terms of logical notions and proving the fundamental axioms of mathematics as theorems of logic. While hugely important in the development of logic, philosophy of mathematics and more broadly of “Early Analytic Philosophy”, the work itself is no longer studied for these topics. As a result the very notation of the work has become alien to contemporary students of logic, and that has become a barrier to the study of Principia Mathematica. We include a series of definitions of notions such as transfinite cardinal numbers, well-orderings, rational and real numbers. These are defined differently in the theory of types of PM than than in axiomatic set theory. 