Learn English – Difference between “sky” and “air”

A plate is a specific type of dish. A dish is generally something that food is eaten or served from. A plate tends to refer specifically to a flat dish that is suitable for holding food that does not have a high liquid content. The other common type of dish is a bowl. A bowl will be similar to a hollow sphere cut in half and is useful for serving soups and other foods with high liquid content which would run off of a plate.

A large plate intended for serving food may be referred to as a platter.

Typically, a canopy is used to provide shade while a roof offers more solid protection; canopies filter and roofs protect. You often hear 'canopy' used to describe the sky-ward protection you experience in a forest or jungle--basically only shade and maybe a little protection from rain. A cave would offer roof-like protection--shade, protection from rain, and protection from big, hard, nasty things that fall from the sky.

These pseudo definitions could be applied to earth's atmosphere in a similar way. Ask, "Does the atmosphere provide a shade-like protection against things from outer space, or does it offer more solid protection?" I think for most of the big, hard, nasty things that fall from outer space that our atmosphere is only a canopy, but if you are specifically talking about types of radiation that our atmosphere completely reflects or absorbs you could claim that our atmosphere (or sky) is a roof.