An aero gramme, also known as an air letter or aerogram, is a type of letter that is both lightweight and foldable, designed for postal delivery via airmail. However, there are many synonyms for this type of letter, including air letter sheets, aerophilately, air letter forms, and air letter envelopes. Additionally, the term "aerogramme" may also be spelled "aerogram" or "aerogramme paper." Regardless of the exact phrasing, all of these synonyms refer to the same type of mail that is specially designed for delivery via air transportation, often with unique postage rates and delivery timelines.