A French scene is a scene in a play of which the beginning and end are marked by a change in the makeup of the group of characters onstage, rather than by the lights going up or down or the set being changed. Identifying the French scene changes is a useful way of breaking a play into discrete sections for ease of directing. An example of a French scene change would be in Hamlet when Ophelia enters near the end of Hamlet's "To be or not to be" soliloquy. Some plays are intentionally written so that the differences between French scenes are distinct, and these may be the only significant breaks, for example if the play is continuous, perhaps without intermission.
The novel J R by William Gaddis is broken into French scenes. These could be called "French chapters." The novel is one continuous chapter, with significant changes in place and character makeup occurring as a result of entrances and exits.