The Free On-line Dictionary of Computing (30 December 2018):

Unix manual page
man
man page
Unix man page

    (Or "man page") A part of Unix's
   extensive on-line documentation.  To read a manual page from
   the Unix command line, type:

   	man [-s
] 

   e.g. "man ftp" (the section number can usually be omitted).
   Pages are traditionally referred to using the notation
   "page(section)", e.g. ftp(1).

   Under SunOS (which is fairly typical), Section 1 covers
   commands, 2 system calls, 3 C library routines, 4 devices
   and networks, 5 file formats, 6 games and demos, 7
   miscellaneous, 8 system administration.  Each section has an
   introduction which can be obtained with, e.g., "man 2 intro".

   Manual pages are stored as nroff source files.  Formatted
   versions are also usually cached.  Man pages for most versions
   of Unix are available on-line in HTML.

   Unix manual page: man(1).

   Linux man pages (http://www.kernel.org/doc/man-pages/).

   Solaris man pages (http://docs.sun.com/app/docs/coll/40.10).

   (2010-01-19)