- 一一九 yīyījiǔ 119Emergency telephone number for reporting fires or other disasters requiring rescue services
- 一一对应 yīyīduìyìng one-to-one correspondenceA relationship where each element in one group corresponds to exactly one element in another group
- 一一映射 yīyīyìngshè bijective map(math) a one-to-one mapping between the elements of two sets where every element of one set is paired with exactly one element of the other
- 不一一 bùyīyī I won't go into detailsLiterary phrase used at the end of a letter to indicate that the writer will not elaborate further or list items one by one.