Deco = art deco = a popular design style of the 1920s and 1930s characterized especially by bold outlines, geometric and zigzag forms, and the use of new materials (as plastic) Decor = decoration consisting of the layout and furnishings of a livable interior. Decoration = something used to adorn, enrich, or beautify. As you can see, they are a nested set of concepts, with the last the most general and the first the most specific.
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