transponder

Etymology

It is a blend from English transmitter + responder,^{[2][3][4][5][6][7]} or, in the analysis of the OED and Oxford dictionaries, of parts of transmit and respond, with the agent suffix -er.^{[8][9][10][11][12]}

Earliest recorded meaning

A device that receives a signal and automatically answers it: 1945, in the American Army & Navy Journal.^[8][12] Merriam-Webster dates it to about 1944.^[3][13]

Semantic evolution

The OED defines the word as a synonym of responder in its radio sense.^[8] Merriam-Webster notes that such sets are used especially to detect, identify and locate objects, and in satellites to relay signals.^[13] The Shorter Oxford and Collins record the telecommunications sense, the receiver and transmitter in a communications or broadcast satellite that relays signals back to earth, from the mid-20th century.^[9][5] The less common spelling transpondor is, according to Merriam-Webster, an alteration influenced by responsor.^[3][4]

Timeline

• 1945 – a unit that receives a signal and automatically responds.^[8][12] Merriam-Webster dates it to about 1944.^[3]
• mid-20th century – the receiver and transmitter of a communications satellite.^[9]

Meanings

Noun

1. A radio or radar transmitter and receiver that sends out a signal of its own automatically when it receives a set signal, used to detect, identify or locate an object such as an aircraft.^{[14][3][13][5]}
2. The unit in a communications or broadcast satellite that receives signals and relays them back to earth.^[5][9]

Related words

• transmitter
• responder
• transmit
• respond

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
3. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b Gove, Philip Babcock, ed. (1961), Webster's Third New International Dictionary of the English Language, Unabridged, Springfield, Mass.: G. & C. Merriam
5. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins
6. ^ The Chambers Dictionary (2014), 13th ed., Edinburgh: Chambers
7. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
8. ^ a b c d Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
9. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
10. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
11. ^ Soanes, Catherine; Stevenson, Angus, eds. (2004), Concise Oxford English Dictionary, 11th ed., Oxford: Oxford University Press
12. ^ a b c Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
13. ^ a b c Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
14. ^ The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin