focal length

noun

: the distance of a focus from the surface of a lens or curved mirror

Examples of focal length in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Evans generally recommends using a wide lens with a focal length between 14 and 24 mm. — Jaclyn Cosgrove, Los Angeles Times, 30 July 2026 Importantly, the lens delivers clear results across the entire frame at most focal lengths, except at 24mm. — Jim Fisher, PC Magazine, 9 July 2026 Maksutov-Cassegrain is a catadioptric design that uses two mirrors to allow a long focal length to fit into a compact optical tube. — Harry Bennett, Space.com, 11 June 2026 Full specs are still under embargo until later, but the Pocket 4P brings back the 1-inch sensor seen in the DJI Pocket 4, with a secondary camera that provides a longer focal length. — Ben Sin, Forbes.com, 15 May 2026 See All Example Sentences for focal length

Word History

First Known Use

1682, in the meaning defined above

Time Traveler
The first known use of focal length was in 1682

Rhymes for focal length

See All Rhymes for focal length

Browse Nearby Words

focalize
focal length
focal plane
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Cite this Entry

“Focal length.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/focal%20length. Accessed 5 Aug. 2026.

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Kids Definition

focal length

noun
: the distance of a focus from the surface of a lens or inwardly-curved mirror

Medical Definition

focal length

noun
-ˌleŋ(k)th How to pronounce focal length (audio)
: the distance of a focus from the surface of a lens or concave mirror
—symbol f

More from Merriam-Webster on focal length

Britannica.com: Encyclopedia article about focal length

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