Where does this definition of focal length come from?
This entry for focal length is sourced from GetWord Corpus, one of the dictionaries and corpora merged into Lughet.
Does focal length appear elsewhere on Lughet?
Yes — focal length appears under other sources or language pairs in Lughet's collection. See the list below.
What is Lughet?
Lughet is a free trilingual dictionary covering nearly five million entries across Uyghur, Chinese, and English, drawn from more than ten source dictionaries and corpora.