Canonization is the act by which a Christian Church declares some deceased person to be a saint, inscribing that person in the canon, or list, of recognized saints.
In the Catholic Church, the act of canonization is now kept to the Holy See and occurs at the conclusion of a long process requiring extensive proof that the person future for canonization lived, and died, in such a way that he or she is worthy to be recognized as a saint. at first, however, individuals were recognized as saints without any formal process, as happened, for instance, in the case of Saint Peter and the Blessed Virgin Mary. Other Christian Churches still follow the older practice
Canonization, whether formal or informal, does not make someone a saint: it is only a declaration that the person is a saint and was a saint even before canonization. It is generally familiar that there are many more saints in heaven than have been canonized on earth.