Anaerobic is a word coming from the Greek word "αναερόβιος" (comprising from the words αν=without, αέρας=air and βίος=life) which literally means living without air, as opposed to aerobic.

In wastewater treatment the absence of oxygen is indicated as anoxic; and anaerobic is used to indicate the absence of a common electron acceptor such as nitrate, sulfate or oxygen.

Anaerobic may refer to:

  • Anaerobic adhesive, a bonding agent that does not cure in the presence of air
  • Anaerobic clarigester, is a form of anaerobic digester
  • Anaerobic contact process, is a type of anaerobic digester
  • Anaerobic digestion, (AD) is the naturally occurring process of anaerobic decomposition harnessed and contained to manage waste and/or release energy.
  • Anaerobic environment, an aquatic environment with little available oxygen - see Hypoxia (environmental)
  • Anaerobic exercise, a form of exercise
  • Anaerobic filter
  • Anaerobic lagoon, used to dispose of animal waste, particularly that of cows and pigs
  • Anaerobic organism, any organism whose redox metabolism does not depend on free oxygen
  • Anaerobic respiration, oxidation of molecules in the absence of oxygen
  • Anaerobic ammonium oxidation, anammox, the microbial process combining ammonium and nitrite.