Dear friend in Christ, Great question. The title is not a reference to medicine but to teaching. A Doctor of the Church is a saint whose writings are particularly outstanding and have significantly helped Catholics understand their faith. The Doctors of the Church have contributed to the intellectual heritage of the Church in a remarkable way. The writings of the Doctors are given special credence in Catholic intellectual and academic tradition although they are not infallible (free from error).
There are 36 Doctors of the Church. Here they are in alphabetical order:
St. Albertus Magnus St. Alphonsus Liguori St. Ambrose St. Anselm St. Anthony of Padua St. Athanasius St. Augustine St. Basil the Great St. Bede the Venerable St. Bernard of Clairvaux St. Bonaventure St. Catherine of Siena St. Cyril of Alexandria St. Cyril of Jerusalem
St. Ephrem St. Francis de Sales
St. Gregory Nazianzus St. Gregory of Narek St. Gregory the Great St. Hilary of Poitiers St. Hildegard of Bingen St. Isidore of Seville St. Jerome St. John Chrysostom St. John Damascene St. John of Avila St. John of the Cross St. Lawrence of Brindisi St. Leo the Great St. Peter Canisius St. Peter Chrysologus St. Peter Damian St. Robert Bellarmine St. Teresa of Ávila St. Therese of Lisieux St. Thomas Aquinas
Doctors of the Church, pray for us!