undetectable

Etymology

It is formed from English un- + detectable.^[1][2] Detectable, recorded from 1655, is from the verb detect and the suffix -able,^[2][1] and the verb goes back to Latin dētegō (“to uncover, expose”), from dē- (“un-, off”) and tegō (“to cover”), from Proto-Indo-European *(s)teg- (“to cover”).^[1]

Earliest recorded meaning

Not able to be detected: Etymonline dates the word to 1789.^[1] The OED's first quotation is later, from the Cornhill Magazine of March 1863.^[2]

Semantic evolution

The adjective rests on the later sense of detect, "to discover, find out", which Etymonline dates to 1756, and not on the verb's first sense, "to uncover, lay bare", recorded from the early 15th century and now obsolete.^[1] The OED records the noun undetectability from 1960, and the adverb undetectably.^[3]

Timeline

• 1789 – not able to be detected.^[1] The OED's first quotation is from 1863.^[2]
• 1960 – the noun undetectability.^[3]

Meanings

Adjective

1. Impossible to detect, notice or discover; escaping observation: The leak was undetectable without special instruments.^[4][5][6]

Word family

• undetectably
• undetectability

Related words

• undetected
• detect
• detectable
• detective

Usage notes

Collins records indetectable as a less common form of the word.^[5][6]

References

1. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
2. ^ a b c d Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press
4. ^ Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
5. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins
6. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org