Number of lines of the Vim window. Normally you don't need to set this. It is done automatically by the terminal initialization code. Also see posix-screen-size. When Vim is running in the GUI or in a resizable window, setting this option will cause the window size to be changed. When you only want to use the size for the GUI, put the command in your gvimrc file. Vim limits the number of lines to what fits on the screen. You can use this command to get the tallest window possible:

:set lines=999

Minimum value is 2, maximum value is 1000. If you get fewer lines than expected, check the 'guiheadroom' option. When you set this option and Vim is unable to change the physical number of lines of the display, the display may be messed up.

(default 24 or terminal height)