Formulas
- Atkinson–Mingarelli theorem
- Atmospheric tide
- Atomic mass
- Atomic orbital
- Augmentation ideal
- Augmented hexagonal prism
- Augmented pentagonal prism
- Augmented sphenocorona
- Augmented triangular prism
- Augmented truncated tetrahedron
- AB magnitude
- ALOHAnet
- AVL tree
- Abel–Plana formula
- Absolute electrode potential