- arachnitis
- arachnophobia
- aralla quinquefolia
- arantius ligament
- arbor
- arborescent
- arborvirus
- arc lamp
- arc-eye
- archenteron
- archicerebellum
- archinephron
- archoplasm
- archostenosis
- arcuate ligament
- arcus juvenilis
- arcus senilis
- arcuspalatogiossus
- area
- area perforata
- area sponglosa
- aregenerative
- arenation
- areolar tissue
- argentaffincelis
- argentic
- argentophil
- argyrism
- aproctia
- aprosopus
- apyretic
- aqueduct
- aqueous humour
- arachnoid space
- aralla papyrifera
- archeblosis
- archespore
- archetype
- archicenter
- archikaryon
- archipallum
- arcus vertebrae
- ardent pulse
- area ceisi
- area opaca
- area vestibularis
- areca
- areolar gland
- argyria
- arhenoplasm
- arhythmic
- army hospital
- Arnoid-Chiarinalformation
- aromatic
- arousal
- arrhenokaryon
- arsenic
- arteria
- arteria fibularis
- arteria hepatica
- arteria renalis
- arteriae oesophagae
- arteriae sigmoideae
- arteriola
- arterionecrosis
- arteriosclerotic vertigo
- arteriovenous aneurysm
- arteritis detormans
- arthraegia
- arthritic calculus
- arthrodesis
- articular facet
- articular surface
- articulator
- artificial respiration
- artificial silk
- aryepiglottic muscle
- ascarid
- asexual cycle
- asexual reproduction
- asphyxia
- assimilation
- assisted respiration
- association area
- astasia
- aster
- asteroid hyalitis
- asthenia
- asthenopia
- astigmatic
- astragalus
- astral mitosis
- astringency
- astrocytoma
- asymbolia
- asymptomatic
- asymptotic solution
- asyndesis
- ataxiaphaxia
- ataxic paraplegia