Chevet in the context of "Basilica of Sant'Apollinare in Classe"

A Lady chapel or lady chapel is a chapel dedicated to Mary, mother of Jesus, particularly one inside a cathedral or other large church. The chapels are also known as a Mary chapel or a Marian chapel, and they are traditionally the largest side chapel of a cathedral, placed eastward from the high altar and forming a projection from the main building, as in Winchester Cathedral. Most Roman Catholic, as well as some Lutheran and Anglican cathedrals still have such chapels, while mid-sized churches have smaller side-altars dedicated to the Virgin.

The occurrence of lady chapels varies by location and exist in most of the French cathedrals and churches where they form part of the chevet. In Belgium they were not introduced before the 14th century; in some cases they are of the same size as the other chapels of the chevet, but in others (probably rebuilt at a later period) they became much more important features. Some of the best examples can be found in churches of the Renaissance period in Italy and Spain.