More than one member of the not domain of prokaryotes.
The term, archaea, that is, is a , and also is less formal a term than Archaea, or even Archaea with the but without the .
See also archaeon, archaeal, , , and domain Archaea. Contrast, though, with Archaean.
For example, one could say, "this archaeon" versus "those archaea". Alternatively, and more formally, one could say, "the Archaea".