What does comae mean?
'Comae' is the plural form of the noun 'coma', but only in its scientific senses — not the medical one. In astronomy, a coma is the diffuse, glowing envelope of gas and dust that sublimates from a comet's icy nucleus as it approaches the Sun; several such envelopes are described as comae. In botany, a coma is a tuft of soft, hairlike bristles, such as those crowning seeds of milkweed or cotton-grass, where comae assist wind dispersal. Because English borrowed these terms from Latin, which took the Greek word kōmē ('hair'), the learned plural keeps its classical shape, pronounced KOH-mee. This makes 'comae' easy to confuse with 'comas', the ordinary plural of the medical coma — a deep state of prolonged unconsciousness. Writers should therefore reserve 'comae' for technical contexts involving comets or plant morphology, and reach for 'comas' everywhere else.
nounThe plural of 'coma' (sense referring to the nebulous envelope surrounding a comet's nucleus, or a tuft of hairlike structures on a seed or plant). It is not the plural of the medical 'coma', which is 'comas'.
- The plural of 'coma' meaning the diffuse cloud of gas and dust surrounding the nucleus of a comet.
- The plural of 'coma' meaning a terminal tuft of soft, hairlike structures, as on certain seeds or the top of a palm or pine.
"As the comet neared the sun, astronomers measured the growing comae of dust and gas around its nuclei."
"Long-exposure photographs revealed two distinct comae surrounding the binary comet's twin nuclei."
"Botanists noted the silvery comae that aid wind dispersal of the seeds."
'Comae' is itself the standard plural of 'coma' in the astronomical and botanical senses; it has no further plural of its own.
"The survey catalogued dozens of comae across the observed comet population."
One word, two plurals: the life-saving medical 'coma' becomes 'comas', but the comet's glowing halo becomes 'comae' — mixing them up is a classic astronomy-paper typo.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of comae
Both senses trace to the ancient Greek kōmē, meaning 'hair' or the mane of a head, adopted into Latin as coma. The astronomical sense arose because a comet's fuzzy envelope was likened to flowing hair, giving rise to the related term 'comet' (Greek kōmētēs, 'long-haired star'). English acquired the word through Latin scientific vocabulary, and technical usage preserves the Latinate plural 'comae' rather than the regularized 'comas'.
Related word forms
How comae is actually used
'Comae' is a technical plural used almost exclusively in astronomy and botany; in everyday writing about unconsciousness, use 'comas' instead. The plural retains the long final vowel of the Greek-derived singular.
Easily confused with comae
A comma is a punctuation mark or a tiny butterfly; comae are the hazy envelopes around comet nuclei or plant tufts, despite the similar spelling.
'Coma' can mean a deep unconscious state (plural 'comas') or a comet's gaseous envelope (plural 'comae'); only the astronomical/botanical sense takes this plural.