Search the whatis database for complete words.
Syntax whatis keyword ...
The whatis database is a set of database files containing short descriptions of system commands for keywords.
The whatis command searches this database and displays the result on standard output.
List all the man(1) commands
$ export LC_ALL='C'
$ whatis ' ' | egrep '\(1\)'|sort
“A man travels the world in search of what he needs and returns home to find it” ~ George Moore
apropos - Search the whatis database for strings.