lambda

Etymology

The OED takes it borrowed from Late Latin lambda, a 4th-century variant of labda, the classical Latin name of the letter, from Ancient Greek λάβδα (lábda), also λάμβδα (lámbda);^[2][3] Barnhart, Merriam-Webster and Collins derive it directly from Greek.^[4][5][6] Some Middle English forms come instead from the late Latin variant lauda, which reflects a later Greek pronunciation.^[2] The Greek name is of Semitic origin,^[5][6][7] from the Phoenician name of the letter,^[2][3] akin to Biblical Hebrew לָמֶד (lāmedh), the name of the twelfth letter of the Hebrew alphabet (lamed),^[4][8][3] which probably meant "ox goad".^[4] Klein notes that the final -a was added because a Greek word cannot end in -d.^[3]

Earliest recorded meaning

The name of the eleventh letter of the Greek alphabet: about 1400, in Mandeville's Travels,^[4] in a manuscript the OED dates before 1425.^[2]

Semantic evolution

From the letter's shape, Middle English surgeons used the word for a bone at the back of the skull, the occipital bone (before 1425), and for the lambdoid suture (about 1475), like Middle French lande;^[2] the modern anatomical sense, the point where the sagittal and lambdoid sutures meet, follows French lambda in Paul Broca's work.^[2] Merriam-Webster takes this sense as a back-formation from lambdoid.^[5] In the 20th century the letter became a scientific symbol and name: the lambda point in physics (1932), a millionth of a litre (1934), a bacteriophage of E. coli (1950), named after the earlier use of kappa for a factor in another bacterium, and the lambda particle (1954).^[2][4]

Timeline

• c. 1400 – the eleventh letter of the Greek alphabet.^[4][2]
• before 1425 – the occipital bone of the skull (obsolete by 1475).^[2]
• c. 1475 – the lambdoid suture of the skull.^[2]
• 1877 – the point where the sagittal and lambdoid sutures meet.^[2]
• 1932 – lambda point, in physics.^[4]
• 1934 – a microlitre, usually written λ.^[2][4]
• 1950 – a bacteriophage of Escherichia coli.^[2] Barnhart dates lambda virus to 1965.^[4]
• 1954 – the lambda particle, a neutral baryon.^[2][4]

Meanings

Noun

1. The eleventh letter of the Greek alphabet (Λ, λ), corresponding to the Latin L.^[6][5][2][8]
2. In anatomy, the point where the sagittal and lambdoid sutures of the skull meet.^[5][2]
3. In physics, the lambda particle, an uncharged, unstable baryon that usually decays into a nucleon and a pion.^[5][2][9]
4. A millionth of a litre; a microlitre.^[2][9][5]
5. In microbiology, a bacteriophage that infects Escherichia coli, much used in research.^[2]

Word family

• lambdacism
• lambdoid
• lambda hyperon
• lambda particle
• lambda point

Related words

• lamed
• alpha

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p q r s Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
4. ^ a b c d e f g h i j Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
7. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
8. ^ a b Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
9. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press