nonsister

Nonsister is an English term that can function as a noun or an adjective meaning "not a sister." In common usage it appears mainly in formal or technical contexts. In everyday speech, speakers usually say "not a sister" or specify the relationship (for example, "my non-sister relative") rather than using the standalone term. In scientific literature, however, "nonsister" appears in compounds such as "nonsister chromatids" or "nonsister chromatid exchange."

In genetics, nonsister chromatids refer to chromatids from homologous chromosomes that are not the two copies of the same chromosome (i.e., not sister chromatids). During meiosis, crossing over typically occurs between nonsister chromatids, allowing exchange of genetic material and increasing recombination. This contrasts with sister chromatid exchange, which involves the two copies of the same chromatid after DNA replication. In texts, "nonsister" is often combined with "chromatid" or "chromatids" to describe interactions in recombination processes. The spelling "non-sister" with a hyphen is also common in some sources; both forms appear in literature, but "nonsister" as a standalone word is less standardized.

Beyond biology, the word may function simply as a negation of "sister" in familial language, but this usage is rare and can be ambiguous. When clarity is required, writers use more specific terms such as "not a sister," "half-sister," "step-sister," or "non-sister relative." The term's primary traction is in genetics and related disciplines, where it helps distinguish chromosomal partners during recombination.