- Adnexa
- Adrenal gland
- Adrenaline
- Adult-onset Still disease
- Advance directives
- Advance medical directives
- Adverse event
- Aerophagia
- Aerosinusitis
- Aerosol
- Aerotitis
- Aerotitis media
- Aetiology
- Afferent
- Afferent nerve
- Afferent vessel
- African tapeworm
- AFP (alpha-fetoprotein)
- AFO (ankle-foot orthosis)
- African tick typhus
- Afterbirth
- Agammaglobulinemia
- Agenesis
- Agent, antihypertensive
- Agent, anti-infective
- Agent, tocolytic
- Agreement, arbitration
- AIDS definition - HIV: health and medical information about HIV and AIDS
- Alpha-fetoprotein (AFP)
- Alpha interferon
- Alb-
- Albinism
- Albino
- Albuginea
- Albumen
- Albumin
- Alcohol, pregnancy
- Aldosterone
- Aldosteronism
- Allele