China 
Africa 
- Anaerobic respiration
- Anaglyph
- Anal
- Analcime
- Analgesia
- Analog
- Analog computers
- Analog device
- Analog filter
- Analog image processing
- Analog multiplier
- Analog signal processing
- Analog signals
- Analog transmission
- Analog-to-digital converter
- Analogue
- Analogue electronics
- Analogue filter
- Analogue switch
- Analogy
- Analyse-it
- Analysis of covariance
- Analysis of variance
- Analysis paralysis
- Analytes
- Analytic continuation
- Analytic element method
- Analytic function
- Analytic geometry
- Analytic semigroup
- Analytic signal
- Analytical balance
- Analytical chemistry
- Analytical hierarchy
- Analytical mechanics
- Analytical quality control
- Analytical techniques
- Analytics
- Analyze
- Analyzers
- Anammox
- Anandamide
- Anaphora
- Anaphylatoxins
- Anaphylaxis
- Anaplastic
- Anaplastic oligodendroglioma
- Anaplerotic
- Anastomosis
- Anastrozole
- Anastylosis
- Anatabine
- Anatase
- Anatexis
- Anatomical landmarks
- Anatomical pathology
- Anatomical planes
- Anatomical variation
- Anatomy
- Anatoxin-a
- Anchor
- Anchor bolts
- Anchor ice
- Anchor plates
- Anchor text
- Anchorage
- Anchoring fibrils
- Ancillary services
- Ancillary statistic
- Ancylostoma duodenale
- Andalusite
- Andersen thermostat
- Anderson localization
- Andesine
- Andesite
- Andorite
- Andradite
- Androgen deprivation therapy
- Androgen receptor
- Androgen suppression
- Androgens
- Android
- Android Runtime
- Androstane
- Androstenedione
- Anecdotal evidence
- Anechoic chambers
- Anemia
- Anemometers
- Anencephaly
- Anesthesia
- Anesthesiologists
- Anesthesiology
- Anesthetic
- Anethole
- Aneurysm
- Aneutronic fusion
- Angina
- Angioedema
- Angiogenesis
- Angiogenesis inhibitors
- Angiogenin
- Angiography
- Angioplasty
- Angiopoietin
- Angiosarcoma
- Angiotensin
- Angiotensin II
- Angiotensin II receptor antagonists
- Angiotensin receptors
- Angle
- Angle bisector
- Angle grinder
- Angle modulation
- Angle of attack
- Angle of incidence
- Angle of parallelism
- Angle of repose
- Angle of view
- Angle plate
- Angle-resolved photoemission spectroscopy
- Anglesite
- Angstrom
- Angular
- Angular acceleration
- Angular aperture
- Angular displacement
- Angular distance
- Angular frequency
- Angular gyrus
- Angular momentum
- Angular momentum of light
- Angular rate sensor
- Angular resolution
- Angular spectrum method
- Angular velocity
- AngularJS
- Anharmonicity
- Anhedonia
- Anhydrides
- Anhydrite
- Anhydroglucose unit
- Anhydrous
- Anilides
- Aniline
- Animal drugs
- Animal glue
- Anion gap
- Anion-exchange chromatography
- Anion-exchange membranes