adverb
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.
彼が遅刻するのは九分九厘間違いない。
It's almost certain he'll be late.
この計画は九分
This plan will succeed in all probability.
noun
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.
準備は九分九厘まで整っている。
Preparations are ninety-nine percent complete.
From 九分九厘 (ku-bu ku-rin), literally 'nine bu nine rin', where 1 bu (分) is one-tenth and 1 rin (厘) is one-hundredth, totaling 99%. The expression figuratively means 'almost 100%'.