What term is used to describe matters having to do with the church or the clergy?

The term that describes matters having to do with the church or clergy is ecclesiastical. This word specifically pertains to church affairs, the governance of the church, and the functions of the clergy. It encompasses the organizational structures, rules, and practices that underpin the religious institution's operation. For instance, ecclesiastical law pertains to the legal system governing church matters, while ecclesiastical authorities refer to those in leadership positions within a church hierarchy.

In contrast, secular refers to matters that are not connected to religion or the church and are part of the worldly, non-religious realm. Religious is a broader term that encompasses all aspects related to religion, but it does not specifically indicate the institutional or administrative side like ecclesiastical does. Finally, spiritual relates more to personal or individual beliefs and the pursuit of one's spiritual life, without necessarily involving organized religion or its clergy. Therefore, ecclesiastical is the most precise term for this context.