China 
Africa 
- Actinobacillus pleuropneumoniae
- Actinobacillus suis
- Actinobacteria
- Actinolite
- Actinometer
- Actinomyces
- Actinomyces israelii
- Actinomyces naeslundii
- Actinomyces viscosus
- Actinomycetes
- Actinomycetoma
- Actinomycin
- Actinomycosis
- Actinoplanes
- Action potentials
- Activated alumina
- Activated carbon
- Activated charcoal
- Activated clotting time
- Activated complex
- Activated protein C
- Activated protein C resistance
- Activating transcription factor
- Activation analysis
- Activation induced cytidine deaminase
- Activation-induced cell death
- Activation-induced cytidine deaminase
- Activator protein 1
- Active ageing
- Active ester
- Active immunity
- Active immunization
- Active immunotherapy
- Active ingredients
- Active lifestyle
- Active listening
- Active metabolites
- Active packaging
- Active placebo
- Active sites
- Active transport
- Active zone
- Activin
- Activin and inhibin
- Activin receptor
- Activin receptors
- Activities of daily living
- Activity theory
- Activity trackers
- Actomyosin ring
- Actus reus
- Acupressure
- Acupuncture
- Acupuncture needle
- Acupuncture points
- Acupuncturist
- Acute HIV infection
- Acute abdomen
- Acute aortic syndrome
- Acute appendicitis
- Acute basophilic leukemia
- Acute behavioural disturbance
- Acute bronchitis
- Acute cerebellar ataxia
- Acute chest syndrome
- Acute cholecystitis
- Acute confusion
- Acute coronary syndrome
- Acute decompensated heart failure
- Acute disease
- Acute disseminated encephalomyelitis
- Acute eosinophilic pneumonia
- Acute exacerbation of chronic obstructive pulmonary disease
- Acute fatty liver of pregnancy
- Acute febrile neutrophilic dermatosis
- Acute flaccid myelitis
- Acute gastroenteritis
- Acute generalized exanthematous pustulosis
- Acute glomerulonephritis
- Acute heart failure
- Acute hemorrhagic conjunctivitis
- Acute hepatitis
- Acute illness
- Acute inflammation
- Acute inflammatory demyelinating polyneuropathy
- Acute intermittent porphyria
- Acute kidney failure
- Acute kidney injury
- Acute laryngitis
- Acute leukemia
- Acute limb ischaemia
- Acute limb ischemia
- Acute liver failure
- Acute lung injury
- Acute megakaryoblastic leukemia
- Acute monocytic leukemia
- Acute motor axonal neuropathy
- Acute muscle soreness
- Acute myelogenous leukemia
- Acute myeloid leukaemia
- Acute myeloid leukemia
- Acute myelomonocytic leukemia
- Acute necrotizing encephalopathy
- Acute necrotizing ulcerative gingivitis
- Acute organ rejection
- Acute otitis media
- Acute pancreatitis
- Acute pericarditis
- Acute phase proteins
- Acute phase response
- Acute promyelocytic leukemia
- Acute psychosis
- Acute pyelonephritis
- Acute radiation syndrome
- Acute rejection
- Acute renal failure
- Acute respiratory failure
- Acute retinal necrosis
- Acute rhinosinusitis
- Acute severe asthma
- Acute sinusitis
- Acute stress
- Acute stress disorder
- Acute stress reaction
- Acute thyroiditis
- Acute toxicity
- Acute tryptophan depletion
- Acute tubular necrosis
- Acute visual loss
- Acvr2a
- Acvr2b
- Acyl CoA
- Acyl CoA dehydrogenase
- Acyl carrier protein
- Acyl chloride
- Acyl coenzyme A
- Acyl coenzyme A dehydrogenase
- Acyl group
- Acyl-CoA
- Acyl-CoA dehydrogenase
- Acyl-CoA oxidase
- Acylation
- Acylation stimulating protein
- Acylcarnitine
- Acyltransferase
- Acylurea
- Adalimumab
- Adam's apple
- Adamantinoma
- Adams Oliver Syndrome