coincidence

英 [kəʊ'ɪnsɪd(ə)ns] 美 [ko'ɪnsɪdəns]

coincidence (n.): c. 1600, "exact correspondence in substance or nature," from French coincidence, from coincider, from Medieval Latin coincidere (see coincide). From 1640s as "occurrence or existence during the same time." Meaning "a concurrence of events with no apparent connection" is from 1680s, perhaps first in writings of Sir Thomas Browne.

2. What an odd coincidence that he should have known your family.: 他居然认识你的家人，真是太巧了。