Words and abbreviations in a command language should have distinctive spelling, so that simple spelling errors will be recognized as such rather than invoking a different command.
Additional Information:
If one command name is DELETE, abbreviated DEL, then another command should not be named DELIVER, with an abbreviation of DELR. Instead, ERASE could be substituted for DELETE, or SEND for DELIVER. When a system has only a few commands, all of those commands should be distinctive. When a system has many commands, it may not be possible to ensure that each is distinctive. In that case, it is important to ensure that any commands that are destructive or time- consuming are made distinctive.