Nucleoids

Part of speech: noun

Definitions

1. A region within a prokaryotic cell containing genetic material, resembling the nucleus of a eukaryotic cell
2. A genetic structure found in some cellular organisms, involved in the storage and replication of DNA
3. A non-membrane-bound area in prokaryotes where chromosomal DNA is located and maintained for cellular functions

Etymology: "Nucleoids" is the plural of "nucleoid," a term for the region inside a bacterial cell where its chromosomal DNA is gathered. The word is built from "nucleo-," the combining form of "nucleus," and the suffix "-oid," from Greek "-oeidēs," meaning "resembling" or "having the form of." Put together, the name describes something that looks like a nucleus without actually being one. That distinction is the whole point of the coinage. A eukaryotic nucleus is enclosed by a membrane, but bacteria lack membrane-bound organelles, so their DNA sits in a looser, unwrapped mass. Biologists needed a name for this structure that signaled both its resemblance to a nucleus and its lack of a membrane, and the "-oid" ending supplied exactly that qualification.