- Asplenium
- Aglaomorpha
- Anogramma
- Azolla
- Arthropteris
- Adiantum
- Amauropelta
- Athyrium
- Acrostichum
- angioedema
- atrophedema
- anasarca
- akinesia
- alalia
- akinesis
- adenosine
- adenosis
- Afrasian
- Afroasiatic
- Afroasiatic language
- Afro_Asiatic
- Afrasian language
- abscise
- apple fritter
- an excuse
- Arizona cypress
- Annona reticulata
- Asimina triloba
- Annona diversifolia
- Annona squamosa
- Annona cherimola
- Annona glabra
- Annona muricata
- adenoidectomy
- adrenalectomy
- aitchbone
- act of terrorism
- Aegean civilisation
- Aegean culture
- Aegean civilization
- anticyclone
- artichoke plant
- artemis
- a design
- an archaeologist
- arthrosporous
- arthropodous
- angioplastic infantilism
- ablatic retinae
- amputating knife