Prokaryote

Unicellular organism lacking a membrane-bound nucleus

A prokaryote (from Ancient Greek πρό pró, meaning 'before'; and κάρυον káruon, meaning 'nut' or 'kernel'), less commonly spelled procaryote, is a cellular organism that lacks a distinct cell nucleus or other membrane-bound organelles. In the earlier two-empire system, prokaryotes formed the empire Prokaryota; in the current three-domain system, based upon molecular phylogenetics, prokaryotes are divided into two domains Bacteria and Archaea. A third domain, Eukaryota, which consists of single- and multi-cellular organisms with nuclei, organelles and complex cellular architecture, is sometimes considered a clade under Archaea in the two-domain system.

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