Aer

Aer is a historical and linguistic root derived from the Greek aēr, meaning air. In English it is not used as a standalone word today, but it appears as a combining form in etymologies and in certain technical terms to indicate air or the atmosphere. The more common modern prefix is aero-, but aer- survives in a few established terms and in botanical names such as aerenchyma, which refers to tissue with air spaces.

Use and examples: English vocabulary frequently employs the aero- prefix to denote air or aviation, as in aerial, aerospace, aerodynamics, aerobic, and aerosol. The distinction between aer- and aero- is largely historical; many contemporary terms use aero-, while aer- appears mainly in specific words borrowed from older traditions or in certain scientific or botanical contexts.

Acronyms and other uses: Aer is also encountered as an acronym in modern usage. AER commonly stands for the American Economic Review, a leading economics journal, and for Annual Equivalent Rate, a standard way of expressing savings account interest in the United Kingdom. Other organizations and concepts may share the same acronym in different contexts.

See also: aerology, aeronautics, aerodynamics, aeroponics.