This blog is directed to homeowners. If you are a builder or an architect, you should probably click on a different GBAGreenBuildingAdvisor.com article.
Homeowners who send questions to GBA sometimes don't know what to call the parts of their building. (If it's a diffuserIn a forced-air heating/cooling system, the diffuser is a register or grille attached to ducting through which heated or air conditioned air is delivered to the living space. In a tubular skylight or an electric light fixture, the diffuser is a cover plate through which scattered light is delivered., grille, register, or duct termination, there's a fair chance that someone will decide to just call it a "vent.") I've rounded up some of the most confusing terms used by builders and architects and clarified their definitions.
Since a drawing can be a handy way to clarify a definition, I made some quick sketches to illustrate my points.