Phrase guide

focal length

noun · 2 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

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1

noun

Meaning 1

A measure of how strongly an optical system converges or diverges light, the inverse of optical power. In the simple case of a single convex lens, it is the distance along the optical axis from the principal plane of the lens to the lens's focal point (where, for instance, the film would be placed in a camera). For more complex or multi-element optical systems, focal length need not correspond to any obvious measurable physical distance.

Definition source: English Wiktionary via Wiktextract

Topics: engineering, natural-sciences, optics, physical-sciences, physics

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

2

noun

Meaning 2

the distance from a lens to its focus

Definition source: Princeton WordNet 3.0

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: focal distance

Antonyms: none provided

Broader terms: distance

History

Etymology

No etymology was provided for this word.

Across languages

Translations

25 source translations are retained for this English entry.

  • Chinese Mandarin: 焦距 (jiāojù) — distance
  • Czech: ohnisková vzdálenost — distance
  • Danish: brændvidde — distance
  • Dutch: brandpuntsafstand — distance
  • Finnish: polttoväli — distance
  • French: distance focale — distance
  • German: Brennweite — distance
  • Greek: εστιακή απόσταση (estiakí apóstasi) — distance
  • Hungarian: fókusztávolság — distance
  • Hungarian: gyújtótávolság — distance
  • Indonesian: jarak pumpun — distance
  • Indonesian: jarak fokus — distance
  • Irish: fad fócasach — distance
  • Japanese: 焦点距離 (shōten kyori) — distance
  • Māori: roa o te ngahunga — distance
  • Māori: roa ngahunga — distance
  • Norwegian Bokmål: brennvidde — distance
  • Norwegian Nynorsk: brennvidd — distance
  • Norwegian Nynorsk: brennvidde — distance
  • Polish: ogniskowa — distance
  • Portuguese: distância focal — distance
  • Romanian: distanță focală — distance
  • Russian: фо́кусное расстоя́ние (fókusnoje rasstojánije) — distance
  • Swedish: brännvidd — distance
  • Tagalog: tingubing haba — distance