Oracle bone and bronze inscriptions show 久 as a figure of a person viewed from behind with a mark on the lower back — suggesting something "held back" or "detained," giving the sense of duration. By the classical period it had fully grammaticalized into the temporal adjective/adverb meaning "long (in time)."

The greeting 好久不见 (hǎo jiǔ bú jiàn), "Long time no see," is one of the most natural ways to reconnect with someone in Mandarin — equivalent to the English phrase (which itself was borrowed from Chinese pidgin English). Watch out: 久 (jiǔ, "long time") is a homophone of 九 (jiǔ, "nine"), so the number 9 carries a lucky connotation of longevity in Chinese culture.