An assistant priest is a priest in

the Anglican and Episcopal churches who is not the senior member of clergy of the parish to which they are appointed, but is nonetheless in priests' orders; there is no difference in function or theology, merely in 'grade' or 'rank'.

Some assistant priests have a "sector ministry", that is to say that they specialize in a certain area of ministry within the local church, for example youth work, hospital work, or ministry to local light industry. They may also hold some diocesan appointment part-time.