gnus-single-article-buffer

gnus-single-article-buffer is a variable defined in `gnus-sum.el'.
Its value is

nil

Documentation:
*If non-nil, display all articles in the same buffer.
If nil, each group will get its own article buffer.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.