The term "apostle's letter" refers to written communications from the early apostles of the Christian church. Synonyms for this phrase include "epistle," "letter of the apostles," and "New Testament letter." These letters provide insight into the teachings and beliefs of the early church and were often written to specific groups or individuals to address theological issues or provide guidance on Christian living. Some of the most well-known apostle's letters include Paul's letters to the Romans, Corinthians, and Galatians, as well as Peter's letters to the churches in Asia Minor. Today, these letters continue to be revered by Christians worldwide and are considered essential to understanding the foundations of the faith.