episcopal = adjective
Episcopalian = noun
Wrong: Tom and Betty go to the Episcopalian Church.
Correct: Tom and Betty are Episcopalians. They attend an Episcopal Church.
The word “episcopal” refers to governance by bishops. The historic episcopate (bishops) continues the work of the first apostles in the Church: guarding the faith, unity and discipline of the Church, and ordaining men and women to continue Christ’s ministry.
An Episcopalian is a person who belongs to The Episcopal Church, which encompasses churches in the United States and 16 countries. These include: Taiwan, Micronesia, Honduras, Ecuador, Colombia, Venezuela, Haiti, Dominican Republic, Virgin Islands, Puerto Rico and Churches in Europe (Austria, Belgium, France, Germany, Italy and Switzerland).
The Episcopal Church is part of the worldwide Anglican Communion, an international association composed of over 80 million people in 44 regional or national churches in more than 160 countries, all in full communion with the Church of England and, more specifically, with the Archbishop of Canterbury.
“e-pis-co-pal lan-guage: Defining Church Terms,” The Rev. Gene Britton, Forward Movement Publications, 2001.