- Alexandrian
 - abyssal zone
 - albatross
 - adolph simon ochs
 - Argonauta argo
 - Argonaut
 - acrocephaly
 - aboriginal
 - alimental
 - Aplodontia rufa
 - agouti
 - abrocome
 - artificial skin
 - answering machine
 - atrioventricular bundle
 - atrioventricular node
 - atrioventricular trunk
 - anteater
 - aquatic mammal
 - aardvark
 - ant bear
 - aplacental
 - African elephant
 - Albers_Schonberg disease
 - abetalipoproteinemia
 - allegheny spurge
 - allegheny mountain spurge
 - abies amabilis
 - acipenser transmontanus
 - appeasement
 - appease
 - assuage
 - andante
 - accelerando
 - allegretto
 - aggrandize
 - aggrandise
 - agony
 - ail
 - acetanilid
 - aspirin
 - acetphenetidin
 - acetanilide
 - acetophenetidin
 - aminopyrine
 - acetylsalicylic acid
 - Anacin III
 - acetaminophen
 - amidopyrine
 - atrocious