How to display line numbers in 'less' (GNU)

Question

What is the command to make less display line numbers in the left column?

Answer 1

From the manual:

-N or --LINE-NUMBERS Causes a line number to be displayed at the beginning of each line in the display.

You can also toggle line numbers without quitting less by typing -N.

It is possible to toggle any of less's command line options in this way.