Africa 
China 
Japan 
MENA 
- Americium-241
- Ames test
- Amesim
- Amethyst
- Amidase
- Amides
- Amidines
- Amidoamine
- Amifostine
- Amikacin
- Amiloride
- Aminals
- Amination
- Amine gas treating
- Amine oxidase
- Amine oxide
- Amines
- Amino acid complex
- Amino acid sequence
- Amino acid synthesis
- Amino acid transporter
- Amino acids
- Amino alcohols
- Amino esters
- Aminoacyl-tRNA
- Aminocaproic acid
- Aminoglycosides
- Aminoguanidine
- Aminolevulinic acid
- Aminomethylphosphonic acid
- Aminopeptidase
- Aminophenol
- Aminophosphonate
- Aminopolycarboxylic acid
- Aminopyridine
- Amiodarone
- Ammelide
- Ammeline
- Ammeter
- Ammonia
- Ammonia borane
- Ammonia emissions
- Ammonia monooxygenase
- Ammonia production
- Ammonia solution
- Ammoniacal nitrogen
- Ammonium
- Ammonium acetate
- Ammonium alum
- Ammonium bifluoride
- Ammonium bisulfate
- Ammonium bromide
- Ammonium carbamate
- Ammonium carbonate
- Ammonium chloride
- Ammonium dihydrogen phosphate
- Ammonium dinitramide
- Ammonium fluoride
- Ammonium hexachloroplatinate
- Ammonium hexafluorophosphate
- Ammonium hydroxide
- Ammonium iron sulfate
- Ammonium lactate
- Ammonium lauryl sulfate
- Ammonium metavanadate
- Ammonium nitrate
- Ammonium oxalate
- Ammonium perchlorate
- Ammonium perrhenate
- Ammonium persulfate
- Ammonium phosphate
- Ammonium polyphosphate
- Ammonium sulfate
- Ammonium sulfide
- Ammonium sulfite
- Ammonium thiosulfate
- Ammonolysis
- Ammoxidation
- Amnesia
- Amnesic shellfish poisoning
- Amnion
- Amniotic fluid
- Amniotic sac
- Amodiaquine
- Amoebas
- Amoebiasis
- Amoebocyte
- Amorphous
- Amorphous calcium carbonate
- Amorphous carbon
- Amorphous ice
- Amorphous metal
- Amorphous silicon
- Amorphous solids
- Amotivation
- Amount of substance
- Ampacity
- Ampere
- Ampere-hour
- Ampere-turns
- Amperometry
- Amphibious
- Amphibious vehicles
- Amphibolite
- Amphidromic points
- Amphipathic
- Amphiphiles
- Amphoteric
- Amphotericin
- Amphoterism
- Ampicillin
- Amplicons
- Amplifier
- Amplitude
- Amplitude amplification
- Amplitude distortion
- Ampoules
- Amps
- Amputation
- Amsacrine
- Amsler grid
- Amygdala
- Amygdalin
- Amygdaloidal
- Amyl alcohol
- Amylase
- Amylin
- Amyloid
- Amyloid beta
- Amyloid cardiomyopathy
- Amyloid plaques
- Amyloidosis
- Amylopectin
- Amylose
- An
- Anabaena variabilis
- Anabasine
- Anabolic
- Anabolic steroids
- Anabolism
- Anabranch
- Anaconda
- Anaerobic
- Anaerobic corrosion
- Anaerobic digestion
- Anaerobic exercise
- Anaerobic glycolysis
- Anaerobic lagoons
- Anaerobic membrane bioreactor
- Anaerobic oxidation of methane