- Abrasive
- Absorption of Light
- Acceptor Level
- Activation energy
- Activation polarization
- Addition Polymerization
- Adhesive
- Allotropy
- Alloy
- Alloy steel
- Alternating Copolymerization
- Amorphous
- Anelastic deformation
- Anion
- Anisotropy
- Annealing
- Anode
- Antiferromagnetism
- Artificial aging
- Atactic
- Athermal Transformation
- Atomic number
- Atomic packing factor
- Atomic vibration
- Austenite