Refers to the fruit or tree; the katakana form クエン is standard. The synonym シトロン is more common in everyday contexts.
See also: シトロン
Citrons are sometimes used for marmalade or candied peel.
Usually written in katakana; the kanji form 枸櫞 is rare.
Rare kanji spelling; learners will almost always encounter the katakana form.
From 枸櫞, the Chinese name for the citron, borrowed with the Sino-Japanese reading くえん.