almost certainly; in all probability; ten to one
Adverbial use expressing very high likelihood; literally 'nine bu nine rin' (99%). Often used with 〜だろう or 〜に違いない.
It's almost certain he'll be late.
This plan will succeed in all probability.
near-completeness; ninety-nine percent finished
Noun use, often in the pattern 九分九厘まで to mean something is almost complete or nearly perfect.
Preparations are ninety-nine percent complete.