Any process that is carried out at the cellular level, but not necessarily restricted to a single cell. For example, cell communication occurs among more than one cell, but occurs at the cellular level. [GOC:go_curators, GOC:isa_complete]
Any biological process, occurring at the level of a multicellular organism, pertinent to its function. [GOC:curators, GOC:dph, GOC:isa_complete, GOC:tb]