China 
Africa 
- Aeroacoustic analogy
- Aeroacoustics
- Aerobatic
- Aerobatics
- Aerobic
- Aerobic denitrification
- Aerobic digestion
- Aerobic fermentation
- Aerobic glycolysis
- Aerobic granulation
- Aerobic organisms
- Aerobic treatment system
- Aerobiology
- Aerodromes
- Aerodynamic center
- Aerodynamic force
- Aerodynamic heating
- Aerodynamics
- Aeroelasticity
- Aerogel
- Aerographene
- Aerographite
- Aeromagnetic survey
- Aeromonas caviae
- Aeromonas hydrophila
- Aeronautical charts
- Aeronautics
- Aeronet
- Aeroponics
- Aerosol mass spectrometry
- Aerosol spray
- Aerosolization
- Aerosolized
- Aerosols
- Aerospace
- Aerospace engineering
- Aerospace manufacturer
- Aerospace materials
- Aerostatic
- Aerostats
- Aerotolerant
- Aesthetics
- Aethalometer
- Afferent
- Afferent arterioles
- Affibody
- Affine combination
- Affine connection
- Affine geometry
- Affine group
- Affine hull
- Affine manifold
- Affine plane
- Affine scaling
- Affine space
- Affine transformations
- Affinity
- Affinity chromatography
- Affinity diagram
- Affinity maturation
- Affinity propagation
- Affordance
- Afforestation
- Aflatoxin
- Aflatoxin B1
- Aflatoxin M1
- African plate
- African swine fever
- African trypanosomiasis
- Aft phase
- Aft phases
- After-rust
- Afterburners
- Afterdepolarization
- Afterimage
- Afterload
- Aftershocks
- Agar
- Agar plates
- Agaropectin
- Agarose
- Agarose gel electrophoresis
- Agbogbloshie
- Age adjustment
- Age-adjusted
- Agenda
- Agenda-setting theory
- Agenesis
- Agenesis of the corpus callosum
- Agent architecture
- Agent-based computational economics
- Agent-based models
- Agent-oriented programming
- AgentSpeak
- Agents
- Ageusia
- Agglutination
- Agglutinin
- Aggradation
- Aggrecan
- Aggregate
- Aggregate base
- Aggregate functions
- Aggregatibacter actinomycetemcomitans
- Aggregation
- Aggregation number
- Aggregation-induced emission
- Aggregative game
- Agile manufacturing
- Agile software development
- Aging
- Aging brain
- Aging in place
- Agitation
- Agitator
- Aglycones
- Agnosia
- Agonist-antagonist
- Agonists
- Agostic interaction
- Agranulocytes
- Agranulocytosis
- Agricultural biotechnology
- Agricultural land
- Agricultural lime
- Agricultural machinery
- Agricultural pollution
- Agricultural waste
- Agricultural water
- Agrivoltaics
- Agrobacterium rhizogenes
- Agrobacterium tumefaciens
- Agrochemicals
- Agroecology
- Agulhas Current
- AhR
- Ailerons
- Air
- Air Quality Health Index
- Air ambulance
- Air barrier
- Air bearings
- Air cargo
- Air changes per hour
- Air classifier
- Air compressor
- Air conditioning
- Air cooling
- Air current
- Air cycle machine