Exotic R4
Donaldson (1983) showed there exists an exotic smooth Differential Structure on 
. Donaldson's result hasbeen extended to there being precisely a Continuum of nondiffeomorphic Differential Structures on .
References
Donaldson, S. K. ``Self-Dual Connections and the Topology of Smooth 4-Manifold.'' Bull. Amer. Math. Soc. 8, 81-83, 1983. Monastyrsky, M. Modern Mathematics in the Light of the Fields Medals. Wellesley, MA: A. K. Peters, 1997.
- Augmented Hexagonal Prism
- Augmented Pentagonal Prism
- Augmented Polyhedron
- Augmented Sphenocorona
- Augmented Triangular Prism
- Augmented Tridiminished Icosahedron
- Augmented Truncated Cube
- Augmented Truncated Dodecahedron
- Augmented Truncated Tetrahedron
- Aureum Theorema
- Aurifeuillean Factorization
- Ausdehnungslehre
- Authalic Latitude
- Autocorrelation
- Automorphic Function
- Automorphic Number
- Automorphism
- Automorphism Group
- Autonomous
- Autoregressive Model
- Auxiliary Circle
- Auxiliary Latitude
- Auxiliary Triangle
- Average
- Average Absolute Deviation