The command you are looking after is "alias". The syntax is:
So basically, alias kait="kate", should do what you want it to do. To display your current aliases, type only alias with no arguments. To remove an alias, use unalias aliasname.
Whatever you use as alias, will be gone when you logout. To make the changes permanently, you've to add your alias line to your .bashrc or .profile at your home directory.