China 
Africa 
- Air density
- Air embolism
- Air entrainment
- Air filters
- Air flow meter
- Air gap
- Air guns
- Air handler
- Air interface
- Air mass
- Air navigation
- Air parcel
- Air pollutant concentrations
- Air pollution
- Air pollution measurement
- Air preheater
- Air pump
- Air purifiers
- Air separation
- Air source heat pump
- Air sparging
- Air stripping
- Air suspension
- Air temperature
- Air traffic control
- Air traffic controllers
- Air traffic management
- Air traffic service
- Air-cooled
- Air-cooled engines
- Air-fuel ratio
- Air-operated valve
- Air-sensitive
- Air-to-cloth ratio
- Airbags
- Airborne
- Airburst
- Aircrack-ng
- Aircraft
- Aircraft cabin
- Aircraft deicing
- Aircraft design
- Aircraft design process
- Aircraft engine
- Aircraft flight dynamics
- Aircraft ground handling
- Aircraft maintenance
- Aircraft manufacturer
- Aircraft noise
- Aircraft parts
- Aircraft pilot
- Aircraft rescue and firefighting
- Aircraft systems
- Airdrops
- Airfield
- Airflow
- Airfoil
- Airfoils
- Airframes
- Airless tires
- Airlift pump
- Airliners
- Airmanship
- Airmass
- Airplanes
- Airport apron
- Airport terminal
- Airports
- Airships
- Airspace
- Airspace class
- Airspeed
- Airspeed indicator
- Airway
- Airway management
- Airway obstruction
- Airway resistance
- Airworthiness
- Airy disk
- Airy stress function
- Airy wave theory
- Ajmalicine
- Ajmaline
- Akaganeite
- Akermanite
- Akinete
- Akka
- Akoma Ntoso
- AlMgSi
- Alabaster
- Alachlor
- Alanine
- Alanine scanning
- Alarm
- Alarm fatigue
- Alarm management
- Alarmones
- Albite
- Albumin
- Albuminuria
- Alcaligenes latus
- Alcian blue
- Alclad
- Alcohol
- Alcohol abuse
- Alcohol consumption
- Alcohol dehydrogenase
- Alcohol dependence
- Alcohol fuel
- Alcohol oxidase
- Alcohol oxidation
- Alcohol sulfotransferase
- Alcohol withdrawal
- Alcoholic liver disease
- Alcoholism
- Alcohols
- Alcu
- Aldehyde dehydrogenase
- Aldehyde oxidase
- Aldehydes
- Aldicarb
- Aldo-keto reductase
- Aldol
- Aldol condensation
- Aldol reaction
- Aldolase
- Aldose reductase
- Aldose reductase inhibitor
- Aldoses
- Aldosterone
- Aldrin
- AlexNet
- Alexander polynomial
- Alexithymia
- Alfalfa
- Algaas
- Algae
- Algae fuel
- Algal blooms
- Algebra
- Algebra homomorphism
- Algebra of sets
- Algebraic
- Algebraic closure
- Algebraic combinatorics
- Algebraic connectivity
- Algebraic curve
- Algebraic expression
- Algebraic extension
- Algebraic function