- Apéry constant
- Apéry constant approximation
- Apéry number
- Apéry, R.
- Arabian mathematics
- Arabic ciphers
- Arabic number system
- Arabic numeral
- Arabic system of notation
- AR (= absolute retract)
- Arachnida
- Arago, D.F.J.
- Arakelov geometry
- Arakelov, S.Yu.(Аракелов,С.Ю.)
- Arakelov theory
- Araki Huzihiro
- araneidan
- Aratus
- arbelos
- arbitrarily great
- elementary subsystem
- elementary sum
- elementary surface
- elementary surgery
- elementary symmetric expression