omega

Etymology

It is partly borrowed from Late Latin omega and partly its source, Ancient Greek ὦ μέγα (ô méga, “great O”),^[2][3][4] made of ὦ (ô), the letter, and μέγα (méga), the neuter of μέγας (mégas, “great”),^[2][5][3] from Proto-Indo-European *meg- (“great”).^[5][3] It was so called because it stood for a long vowel, in contrast with omicron, "little O".^[3][4][2] Barnhart and Etymonline describe it as Medieval Greek, although the name itself is classical.^[4][3] Skeat relates the Greek adjective to mickle.^[6]

Earliest recorded meaning

The last of a series, the end or final development, chiefly in contrast with alpha: a1398, in John Trevisa's translation of Bartholomaeus Anglicus.^[2] Etymonline and Barnhart date the word to about 1400.^[3][4]

Semantic evolution

The figurative use comes from the Book of Revelation, where God is "Alpha and Omega, the beginning and the ending";^[7][3] Weekley quotes the early English rendering "I am alpha and oo, the bigynnyng and endyng".^[8] The word is recorded as the name of the Greek letter only from 1599 in the OED (the early 16th century in the Shorter Oxford).^[2][9] Johnson (1755) called it simply the last letter of the alphabet, "therefore taken in the Holy Scripture for the last".^[7] Astronomers have used it since 1754 to name the 24th star of a constellation.^[2] In particle physics it named various hyperons from 1953, then a neutral meson (1961) and the negatively charged omega minus (1962), first in a paper by Murray Gell-Mann.^[2] In cosmology it has meant, since 1976, the ratio of the actual density of the universe to the critical density.^[2]

Timeline

• a1398 – the last of a series, the end.^[2]
• 1520s – used figuratively for the last of anything.^[3]
• 1599 – the name of the last Greek letter.^[2]
• 1754 – (astronomy) the 24th star of a constellation.^[2]
• 1961 – (physics) the omega meson.^[2]
• 1962 – (physics) the omega-minus particle.^[2]
• 1976 – (cosmology) the density parameter of the universe.^[2]

Modern meaning

Noun

1. The 24th and last letter of the Greek alphabet (Ω, ω), originally a long open O.
2. The last of a series; the end, as in alpha and omega, the beginning and the end.
3. (physics) An omega meson or an omega-minus hyperon.
4. (cosmology) The ratio of the actual density of the universe to the critical density.

Adjective

1. (chemistry) Relating to or being the end group or position in a chain, as in omega oxidation.

Word family

• omega-3 fatty acid
• alpha and omega

Related words

• alpha
• omicron
• mega-
• mickle

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
6. ^ Skeat, Walter W. (1911), A Concise Etymological Dictionary of the English Language, new ed., Oxford: Clarendon Press
7. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
8. ^ Weekley, Ernest (1921), An Etymological Dictionary of Modern English, London: John Murray
9. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press