In some districts of The Lutheran Church - Missouri Synod, there is an office of "Deacon." It's a new thing and only in some Districts (although the Synod recognizes it). It's entirely unrelated to the older office of Deaconess; they have little to nothing in common.
Deaconess in the LCMS began in 1922. They are women (only) - there is no "Deacon" equal. They are trained at the two seminaries along side of men studying to be pastors (it's fairly common for they to be husbands and wives). They have distinctive vestments/uniforms. They are typically full time and are paid. They assist pastors and others in ministry but do not lead or participate in the worship service in any way. While their duties may be similar to Director of Evangelism or Director of Christian Education or Director of Music or other (new) officies, their ministry can be very broad. They can also work for districts or synod... at times as foreign missionaries, not only in parishes.
Deacon in the LCMS began very recently and exists only in some districts. It is one form of Lay Minister (there are several). They take 10 courses (college-level) taught locally by the District usually by pastors authorized to do so. They must serve under a pastor and usually serve as a kind of Assistant Pastor in the parish usually part-time and nearly always as a volunteer, rarely paid. They can lead the entire service, including preaching the sermon but only as authorized and supervised by their supervisor (the pastor to whom they are associated) but in most cases this is only when the pastor is away for some reason but sometimes for Advent and Lenten services or other special times. Sometimes the Deacon leads the Sunday Worship but the Pastor does the sermon and Sacrament, the two serving together on Sundays. In a few cases, they may serve alone in a very small congregation (of which the LCMS has MANY - typically in rural or inter-center areas) again under a supervising pastor but in a different parish. This function is currently controversial in the LCMS, some Districts welcome this (including mine), some don't permit it.
Functionally, the two MAY be similar (it depends on the setting) but often are very different. Deaconesses are better trained, usually full time and salaried. And they don't serve in the worship service. Deacons are usually part time, volunteers, and always directly supervised and clearly under a pastor.
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