This is a brief introduction to the WJ21 Bridge bidding system: a modified Polish Precision in which we incorporate the best ideas of the popular “Two-Over-One” American bidding system when opening in the major suits. This explains the name WJ21 given to the system. The initials “WJ” come from Polish “Wspólny Język”, words that means “Common Language”. It is a popular bidding system developed in the 1960's in Poland. At the same time, the Two-Over-One is a popular adaptation to the standard bidding system, developed probably in the 1970's in North America and became a very popular approach at the beginning of the 21st Century. Placing both systems together, we obtain our WJ21: an acronym of "Common Bridge Language in the 21st Century". Our main goals in writing this book firstly is to search for consensus on the best of Polish and American bidding systems and, secondly, to try to popularize the Polish Precision within the American Bridge players.