Chapelle rayonnante (apse chapel)

A chapelle (chapel) attached to and accessible from the chœur (choir) or the déambulatoire (ambulatory); in plan (Wikipedia) they are indicated in grey.
The bigger the church, the more radiating apse chapels can be attached to it.
On the picture the chapelles rayonnantes of the Sacré-Cœur in Paray-le-Monial.
See also absidiole.

Chapelle rayonnante - Wikipedia

Sacré-Cœur - Paray-le-Monial