The grades for commercial windows (and all windows) are set by the North American Fenestration Standard and are as follows:
Residential [R]:  For houses/duplexes sheltering one or two families.
Light Commercial (LC): Low- and mid-rise apartment complexes and commercial buildings.
Commercial Windows (CW): For use in low- and mid-rise structures that necessitate higher load tolerance. They must meet minimum durability standards and not exceed deflection limits.
Architectural Windows (AW): For mid- and high-rise structures placed under the most atmospheric and load stresses. They are subject to rigorous standards and testing.