1. formal letters, especially those in the New Testament of the Bible written by apostles
Usage: often capitalized when referring to biblical texts
2. any formal or instructive letters
Usage: literary or formal usage

Examples

• The Epistles of Paul are important texts in Christian theology.
• Students studied the various epistles in the New Testament.
• The scholar wrote lengthy epistles to his colleagues about his research.
• Many of the epistles contain moral and spiritual guidance.
• The professor assigned readings from several biblical epistles.
• Her epistles to the editor were always thoughtfully written.
• The apostolic epistles shaped early Christian doctrine.