Alias a complicated command with a short one. For example:
xsel > alias cleansis "sisclean clean_method=2" cleansis == sisclean clean_method=2
Note that the double quotes are necessary, otherwise the parser will think that clean_method is a parameter for alias, rather than part of the alias.
With no arguments, alias lists the currently defined aliases; with just a name, it shows that alias. Aliases last for the current session.