Extracellular refers to anything that is located or occurs outside of living cells. Some synonyms for extracellular that can be used interchangeably include interstitial, intercellular, and extraplasma. Interstitial refers to the spaces between cells, while intercellular refers to the materials that are located between cells, such as signaling molecules. Extraplasma is another synonym for extracellular and is more commonly used in microbiology to describe chemical reactions or activities that take place outside of the bacterial cells. Overall, these synonyms can be useful to add variety and nuance to scientific writing that involves the extracellular environment.