Acellular is a term used to describe organisms or structures that do not contain cells or are not composed of cells. Some synonyms for acellular include non-cellular, cell-free, and acellularized. Other possible synonyms include non-living, devoid of cells, and lacking in cellular components. Additionally, terms like non-biological, non-organic, and inert can be used to describe acellular structures that are not alive or made up of living components. In the medical field, acellular may also be referred to as non-immunogenic, which means it does not provoke an immune response. Whatever the specific context may be, there are numerous ways to describe and categorize acellular structures and substances.