also: エアー · エヤー
noun
Katakana noun for air, especially air in tires, equipment, products, or compounds. For ordinary atmospheric air or the mood of a place, 空気 is usually more natural.
タイヤにエアを入れた。
I put air in the tire.
このポンプでエアーの量を調整できます。
You can adjust the amount of air with this pump.
Means the sky, not air as a substance; use エア or 空気 when referring to air itself.
A katakana word. No language of origin is specified, so the exact borrowing history is not stated here.