en > eu 
halabeharrez, kasualitatez, txiripaz; ustekabean, ezustean; menturaz, deskuiduan
we met by chance in Dublin: Dublinen ezagutu genuen elkar, kasualitatez
as if by chance: ustekabean
if by chance you see her, tell her I'm waiting: deskuiduan ikusten baduzu, esaiozu zain nagoela