- arbitrary force system
- arbitrary Lagrangian-Eulerian computing methods
- arbitrary projection
- arboreal hypergraph
- arborescence
- arborescence
- arboricity
- arc
- arc coordinate
- arch
- Archimedean absolute value
- Archimedean axiom
- Archimedean class
- Archimedean equivalent
- Archimedean equivalent on a lattice-ordered semigroup
- Archimedean extension
- Archimedean lattice-ordered group
- Archimedean lattice-ordered group
- Archimedean lattice-ordered ring
- Archimedean lattice-ordered ring
- Archimedean ordered field
- Archimedean ordered field over a subfield
- Archimedean ordered group
- Archimedean ordering
- Archimedean order semigroup