The word “ecclesiae” is the plural of “ecclesia.”
There are many synonyms to use for the word believer, which is the most common word for a person who has "converted" to follow Jesus. I have chosen "Jesus follower(s) or follower(s) of Jesus instead of the word believer in these presentations to allow the reader an opportunity to move away from the idea of believer which conjures up the possible thought of "ascent" to a set of doctrines that have been assembled by different groups over the centuries and show up in this day and age as a set of statements posted on web sites and other written material. These sets of beliefs are suggested by many as the ones that one should ascent to so that upon death the one who assents can go to heaven, i.e., just believe and you are good to go. Jesus followers/followers of Jesus suggest an action that one should take. Remember, Jesus told his disciples to follow him. Yes, belief is important, but one must move beyond belief to action.
(See "Discipleship" Dictionary of Jesus and the Gospels. 182-188.)