Glass and glazing measured separately?

Glass and glazing are measured separately.
查字典大致上可知 “Glass”和”glazing”都與玻璃有關，查美國Website，這兩個字還真是常連用 – 之前我也不知。
are measured separately：(這兩件事)是會被分別評估(衡量)。
查Longman
Glass:
transparent material [uncountable] a transparent solid substance used for making windows, bottles etc
a glass bowl
a piece of broken glass
pane/sheet of glass (=a flat piece of glass with straight edges)
the cathedral’s stained glass windows been used to fill windows
Glazing:
glass that has been used to fill windows.
至於glass與glazing有何不同(應有些不同)?太專業了!(我有稍微查一下美國website，但沒查到)