China 
Africa 
- Anionic polymerization
- Anisodamine
- Anisometropia
- Anisotropic
- Anisotropic diffusion
- Anisotropic filtering
- Anisotropy
- Anisotropy energy
- Ankaramite
- Ankerite
- Ankle
- Ankle replacement
- Ankle-brachial index
- Ankylosing spondylitis
- Ankylosis
- Annatto
- Annealing
- Annexin
- Annexin a5
- Annite
- Annotations
- Annual growth rate
- Annular fin
- Annulation
- Annulene
- Annulus
- Anode
- Anode ray
- Anodic bonding
- Anodic protection
- Anodized
- Anodizing
- Anomalous diffusion
- Anomalous photovoltaic effect
- Anomaly
- Anomaly detection
- Anomaly-based intrusion detection system
- Anonymous functions
- Anorexia
- Anorthite
- Anorthoclase
- Anorthosite
- Anosmia
- Anoxic
- Anoxic waters
- Anoxygenic photosynthesis
- Anserine
- Answer set programming
- Ant
- Ant colony optimization
- Ant colony optimization algorithms
- Antacids
- Antagonists
- Antarctic Plate
- Antarctic ice sheet
- Antarctic sea ice
- Antarctica
- Antecedent moisture
- Antenna
- Antenna array
- Antenna boresight
- Antenna complex
- Antenna diversity
- Antenna effect
- Antenna efficiency
- Antenna factor
- Antenna feed
- Antenna measurement
- Anterior chamber
- Anterior chamber angle
- Anterior cingulate cortex
- Anterior communicating artery
- Anterior fontanelle
- Anterior inferior iliac spine
- Anterior longitudinal ligament
- Anterior olfactory nucleus
- Anterior pituitary
- Anterior segment
- Anterior talofibular ligament
- Anterior tibial artery
- Anterograde amnesia
- Anthelmintics
- Anthocyanidins
- Anthocyanin
- Anthophyllite
- Anthracene
- Anthracite
- Anthracyclines
- Anthranilic acid
- Anthraquinone
- Anthraquinones
- Anthrone
- Anthropometry
- Anthroposphere
- Anti-IgG
- Anti-VEGF
- Anti-aliasing
- Anti-aliasing filter
- Anti-foaming agent
- Anti-fog
- Anti-fouling paint
- Anti-graffiti coating
- Anti-immunoglobulin
- Anti-inflammatory
- Anti-lock braking system
- Anti-nuclear
- Anti-nuclear movement
- Anti-nuclear protests
- Anti-patterns
- Anti-reflective coating
- Anti-roll bar
- Anti-scatter grid
- Anti-spam
- Antiandrogens
- Antiarrhythmic
- Antibiotic prophylaxis
- Antibiotic resistance
- Antibiotic sensitivity
- Antibiotics
- Antibodies
- Antibody
- Antibody mimetics
- Antibody-dependent cell-mediated cytotoxicity
- Antibody-drug conjugate
- Antibonding
- Antibonding molecular orbital
- Anticaking agents
- Anticancer
- Antichains
- Anticholinergics
- Anticlines
- Anticoagulants
- Antidepressants
- Antiderivative
- Antidiarrheals
- Antidromic
- Antidunes
- Antiemetics
- Antiferroelectric
- Antiferroelectricity
- Antiferromagnetism
- Antifolates
- Antifreeze
- Antifreeze proteins
- Antifungal
- Antigen presentation
- Antigen processing
- Antigen-antibody interaction
- Antigenic drift
- Antigenic shift