China 
Africa 
- ATO
- ATP
- ATP citrate lyase
- ATP hydrolysis
- ATP sulfurylase
- ATP synthase
- ATPG
- ATPase
- ATR
- ATRP
- AUDIT
- AUV
- AVC
- AVI
- AVIRIS
- AVL
- AVO
- AVS
- AVX-512
- AWD
- AWG
- AWGN
- AWOS
- AWS
- AWS Lambda
- AWT
- AXL
- Aarogya Setu
- Ab initio methods
- Abacus
- Abandoned mines
- Abandoned wells
- Abaqus
- Abbe refractometer
- Abbe sine condition
- Abbreviated Injury Scale
- Abdomen
- Abdominal aortic
- Abdominal cavity
- Abdominal muscles
- Abdominal obesity
- Abdominal trauma
- Abdominal wall
- Abductive reasoning
- Abductor digiti minimi
- Abductor hallucis
- Abductor pollicis brevis
- Abductor pollicis longus
- Abelian group
- Abelian lie group
- Aberration
- Abietane
- Abietic acid
- Abinit
- Abiotic
- Abitibi Greenstone Belt
- Ablation
- Ablation zone
- Abnormal grain growth
- Above sea level
- Abrasion
- Abrasive flow machining
- Abrasive jet machining
- Abrasive machining
- Abrasive saws
- Abrasives
- Abraxane
- Abrin
- Abscess
- Abscisic acid
- Abscissa
- Abscopal effect
- Absolute
- Absolute angular momentum
- Absolute configuration
- Absolute convergence
- Absolute geometry
- Absolute risk
- Absolute risk reduction
- Absolute rotation
- Absolute scale
- Absolute space
- Absolute temperature
- Absolute value
- Absolute zero
- Absolutely continuous
- Absolutely convergent
- Absolutely integrable function
- Absorbance
- Absorbed dose
- Absorbers
- Absorbing
- Absorptance
- Absorption
- Absorption coefficient
- Absorption cross section
- Absorption edge
- Absorption heat pump
- Absorption law
- Absorption of water
- Absorption refrigerator
- Absorption spectra
- Absorption spectroscopy
- Absorptivity
- Abstract algebra
- Abstract data types
- Abstract differential equation
- Abstract interpretation
- Abstract state machines
- Abstract syntax
- Abstraction
- Abstraction layer
- Abundance
- Abutments
- Abyssal plains
- Acanthamoeba keratitis
- Acanthite
- Accelerated aging
- Accelerated approval
- Accelerated curing
- Accelerated failure time model
- Accelerated life testing
- Accelerated solvent extraction
- Acceleration
- Accelerator
- Accelerator-driven subcritical reactor
- Accelerograph
- Accelerometers
- Accent lighting
- Acceptability
- Acceptable daily intake
- Acceptable quality limit
- Acceptance angle
- Acceptance sampling
- Acceptor
- Access Point Name
- Access control
- Access control matrix
- Access structure
- Access time
- Accessibility
- Accessible
- Accessible housing
- Accessible surface area
- Accessible toilet
- Accession numbers
- Accessory pigments
- Accident
- Accident analysis
- Accident investigation