Envelope (french), when applied to painting - particularly the work of Claude Monet - refers to how light and atmosphere surround and are distributed evenly over the composition. It must be noted that objects are not restricted and constrained by the light, rather the light <Read More Below>
is subtly applied evenly across the canvas. 'Envelope' was a concept that Monet developed, and the term is applied to the effect of the same light spread over an object at different times during the day. It is important to not that this light had to be constant and evenly spread/distributed across the surface of the painting.