The Air Around You
It is the condition Earth's atmosphere at a particular time. Weather changes frequently and never stops. It is more constant in some places than the others. In a desert the weather will stay dry and hot for the majority of the time. In a place like North Carolina the weather is almost never the same for more than a couple of days.
It is the envelope of gases that surrounds the Earth. The atmosphere does change over time. It takes many years to even have a noticeable change. Earth's atmosphere is made up of 78% nitrogen, 21% oxygen, and all other gases make up 1%.
It is a form of oxygen that has 3 oxygen atoms instead of the usual 2. Ozone is essential for most life on Earth. If ozone did not filter most UV radiation and all of the rays hit Earth, our planet would be uninhabitable for many living organisms.
It is water in the form of gas. Water vapor is invisible and is not the same as steam. Steam is made up of tiny droplets of water. The amount of water vapor in the air varies frequently. Water vapor is what causes humidity, clouds and precipitation.