The last post traced cometa/comet back to the Greek word kome that meant ‘the kind of hair that grows on a person’s head.’ Latin borrowed Greek kome, keeping its meaning but changing its form slightly to coma. Not surprisingly, the ancient Romans took to using coma figuratively for things like ‘foliage, grass, plant stalks,’ and even poetically for ‘rays of light.’ Modern scientists have followed in that tradition, with one meaning of coma being, the definition of the American Heritage Dictionary, ‘A diffuse, comet-shaped image of a point source of light or radiation caused by aberration in the optical system.’ In astronomy a coma is, as the 1913 Webster’s Revised Unabridged Dictionary explained, ‘The envelope of a comet; a nebulous covering, which surrounds the nucleus or body of a comet.’
Scientific Spanish shares those usages, but note that the Spanish coma that parallels English comma is a different word (and notice that the double consonants that English has maintained sometimes allow us better etymological clues than the corresponding simplified consonants in Spanish). Coma/comma comes from Greek komma, which mean ‘a piece cut off,’ from the verb koptein ‘to cut.’ The Greeks used the term in grammar to designate ‘a short clause,’ and we’ve reapplied the term to the punctuation mark that sets off a short group of words.
Also different is the coma that means ‘A state of profound insensibility from which it is difficult or impossible to rouse a person.’ It comes from Greek koma ‘deep sleep.’
© 2013 Steven Schwartzman