Which term describes metabolic processes that occur in the absence of oxygen?

The term that describes metabolic processes occurring in the absence of oxygen is "anaerobic." This type of metabolism relates specifically to how cells produce energy without the use of oxygen. During anaerobic processes, glucose is usually converted into energy through pathways such as glycolysis, which yields energy in the form of ATP (adenosine triphosphate) and results in byproducts like lactic acid or ethanol, depending on the organism and conditions.

In contrast, aerobic processes require oxygen and are typically more efficient at producing ATP compared to anaerobic processes. Oxidative processes often refer to metabolism involving oxygen to produce energy, which supports this distinction further. The term "fermentative" is related to processes like fermentation, which is indeed a form of anaerobic metabolism but usually describes specific pathways or processes within anaerobic environments. However, "anaerobic" is the broader term that encompasses all metabolic activities that do not utilize oxygen for energy production. This comprehensive definition makes "anaerobic" the most accurate answer to the question posed.