Is it permissible to shorten the prayer without combining it, or to combine it without shortening it?

A traveler, for whom shortening the prayer is permissible, is recommended to shorten the four-rak'ah prayers. It is also permissible for him to combine prayers that share a time, either by advancing or delaying them. There is no necessary connection between combining and shortening prayers. As for a resident, it is not permissible for him to shorten prayers or combine them, except in specific cases.