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
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Functionality: Being a prime lens, features are minimal beyond the aperture and focal length. James Abbott, Space.com, 23 May 2025 This made the humpback’s focal length—the distance between the eye’s lens and retina—shorter than expected, as Bolin tells bioGraphic’s Marina Wang. Margherita Bassi, Smithsonian Magazine, 21 May 2025 This system provides an equivalent focal length of 200mm, which would require a really big lens on a standard camera. Eric Zeman, PCMAG, 2 Mar. 2025 Longer focal length usually indicates sharper eyesight, so this was one sign that humpbacks may have poor vision. Margherita Bassi, Smithsonian Magazine, 21 May 2025 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

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Cite this Entry

“Focal length.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/focal%20length. Accessed 4 Jul. 2025.

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
: the distance of a focus from the surface of a lens or concave mirror
symbol f

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