一旦

in case (sth happens) / if / once (sth happens, then...) / when / in a short time / in one day

one / single / a (article) / as soon as / entire; whole; all; throughout / "one" radical in Chinese characters (Kangxi radical 1) / also pr. [yao1] for greater clarity when spelling out numbers digit by digit

dawn / morning / daybreak / day / dan, female roles in Chinese opera (traditionally played by specialized male actors)