Bypass doors are composed of two doors normally that slide past each other in the door opening. Since there are less doors used than in a Bifold of the same size, each door is normally wider, For instance, a 6' wide closet would have two 3' (36" ) wide doors to make up the width. In some special circumstances, you can also use three or more doors, with a custom installation.
a thing to also remember is when using a Bypass door installation, the opening may have to be undersized slightly, to allow for an overlap, or make one of the doors wider, Example, using a 32" or 30" wide door for a 5' wide opening.