wàn​yī HSK4

just in case

万一 萬一 wàn​yī
just in case adverb
Used to express a low-probability event or hypothesis, usually for something undesirable; in the unlikely event that; if by any chance.

What if I'm wrong?

contingency
A possible but unlikely event or accident; an eventuality.
one ten-thousandth
(bound form) A very small percentage; literally one part in ten thousand.

Frequency

Movie subtitles
28.8 per million appears in 12% of films

Details

HSK 2.0
Level 5
HSK 3.0
Level 4

Sources

Frequency data
SUBTLEX-CH