Ecclesiological: “of or relating to the understanding, doctrine, or concept of the church”
(e.g. “Church architecture has enormous ecclesiological significance.”)
Ecclesiastical: “of or relating to the church as an established institution”
(e.g., “Our church follows an ecclesiastical calendar.”)
Ecclesial: “of or relating to the church or to the church's nature”
(e.g., “Christian existence is ecclesial existence.”)
There. Now we know.
The difference between ecclesiological, ecclesiastical, ecclesial, ecclesiastes, ecclesia, ecclesiology, ecclesiologist