What does chiasmata mean?
Chiasmata is the plural of chiasma, a word with two principal scientific senses. In genetics, chiasmata are the X-shaped points where pairs of homologous chromosomes physically link and exchange segments during meiosis — the process that produces eggs and sperm. These crossovers are essential to sexual reproduction, because they shuffle parental genes so that offspring inherit novel combinations of traits. The word's second sense, older and more general, refers simply to any crossing or X-shaped intersection, especially of nerve fibres, as in the optic chiasma where the visual pathways cross in the brain. Both meanings descend from the Greek letter chi (X), reflecting the distinctive cross shape. Chiasmata is a technical plural used almost exclusively in scientific writing — biology textbooks, research papers, and medical texts — and is rarely encountered outside those fields. Its singular, chiasma, follows Greek-style pluralisation, though anglicised forms such as chiasmas also occur.
Plural of chiasma: the X-shaped points at which homologous chromosomes exchange genetic material during meiosis.
"The frequency of chiasmata varies between chromosomes and species."
This is the dominant sense in modern usage, confined largely to genetics and cytology.
Plural of chiasma: crossings or intersections of anatomical structures, especially nerve fibres, forming an X-shape.
"The surgeon carefully mapped the chiasmata of the optic pathways."
Chiasmata is itself a plural noun (the plural of chiasma), following the Greek pattern; the anglicised plural 'chiasmas' also occurs but is less common in technical writing.
"Several prominent chiasmata were visible under high magnification."
Every one of us exists because chiasmata shuffled our parents' genes — those tiny X-shaped crossover points are why no two people (identical twins excepted) are ever genetically alike.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chiasmata
Chiasmata comes from the Greek khiasma, meaning a thing shaped like the letter chi (X), itself derived from chi, the twenty-second letter of the Greek alphabet whose capital form resembles an X. The word entered English via New Latin as chiasma, retaining the Greek-style plural chiasmata. Its cognates include the rhetorical term chiasmus, which describes a reversed parallel structure in speech or writing, and the adjective chiastic.
Related word forms
How chiasmata is actually used
Strictly a plural form; the singular is 'chiasma' (plural also sometimes rendered 'chiasmas'). The term belongs chiefly to technical registers — cytogenetics, cell biology, and anatomy — rather than everyday speech. In genetics contexts it almost always appears in discussions of meiosis and recombination.
Easily confused with chiasmata
A chiasmus is a rhetorical figure in which words or ideas are repeated in reverse order, while chiasmata is the plural of chiasma, most often referring to points of chromosome crossover or anatomical crossings.