What does 暗算 mean?
暗算 is a Japanese noun meaning “mental arithmetic” in English. It is written as 暗算 in kanji, あんざん in hiragana, and anzan in romaji. This word is part of JLPT N1 vocabulary.
Example sentence
彼は暗算が出来るほど頭が良くない。
He's not smart enough to add numbers in his head.