Pane

A pane of stamps is normally what people would see and think as being a sheet. But philatelists only use "sheet" for the full printed sheet as it comes off a printing press. If you've ever seen a commercial printing press, they have been very large machines for a long time. That size allowed efficiency; there have only been a few cases where a lack of them made it necessary to only print a few designs at one time on a small sheet of paper.

So, that full printed sheet is then normally cut into panes and that is what everyone normally sees being sold across the post office counter today. There has never been a set scheme of dividing sheets into panes except perhaps to fit postal clerks's storage drawers. There have been all different sizes of panes, besides, either in terms of overall size or number of stamps included. Sometimes high values were released with fewer stamps per pane since there was less of a need for those high values. 

