In the New Testament, what word is used to identify letters the disciples sent to each other?

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In the New Testament, the word used to identify letters the disciples sent to each other is "epistle." The term "epistle" is derived from the Greek word "epistolē," which means a letter or a message. The disciples, such as Paul, Peter, and John, wrote these epistles to communicate with early Christian communities and to address various theological, doctrinal, and practical matters.

If you are looking for specific epistles in the New Testament, here are the letters written by the disciples:

1. Paul's Epistles: Romans, 1 Corinthians, 2 Corinthians, Galatians, Ephesians, Philippians, Colossians, 1 Thessalonians, 2 Thessalonians, 1 Timothy, 2 Timothy, Titus, and Philemon.
2. Peter's Epistles: 1 Peter and 2 Peter.
3. John's Epistles: 1 John, 2 John, and 3 John.
4. James' Epistle: The Book of James.
5. Jude's Epistle: The Book of Jude.
6. Hebrews: Although the authorship of Hebrews is uncertain, it is often included in the collection of New Testament epistles.

To find references to these epistles in the New Testament, you can refer to the specific chapters and verses indicated in your Bible or use online resources or study guides that provide detailed information about the books of the New Testament.