adverb
by chance; coincidentally; as it happens
Used when something happens unexpectedly or without planning, often with a nuance of fortunate or surprising coincidence.
偶然にも、同じ電車に乗り合わせた。
By chance, we happened to be on the same train.
偶然にも、彼の誕生日に再会した。
Coincidentally, we met again on his birthday.