- anaerobicWithout oxygen; especially of an environment or organism.
- analgesicA drug used to reduce and manage pain, especially without inducing a loss of other sensation.
- anhedoniaThe inability to feel pleasure from activities usually found enjoyable, such as exercise, hobbies, music, sexual activities or social interactions.
- anergyDilute or disorganized energy, which cannot be transformed into work; bound energy
- anuranAny amphibian of the order Anura: any frog (narrow sense) or toad.
- an-not; used to make words that have a sense opposite to the word (or stem) to which the prefix is attached. Used with stems that begin with vowels and "h".
- anacrogynousProducing archegonia from cells other than the apical cell of a reproductive branch.
- anapsidPertaining to the group of reptiles whose skulls do not have openings near the temples, originally considered as a specific subclass
- anidolicPertaining to nonimaging transfer of light, particularly in the domain of indoor natural lighting.