Even odds; a fifty-fifty chance; an even match where neither side has a clear advantage.
テストの結果は五分五分だと思っていたが、思ったよりできた。
I thought the test would be fifty-fifty, but I did better than expected.
勝敗は五分五分で、最後の一投にかかっている。
The outcome is even; it all depends on the final throw.
彼と私の意見は五分五分で、どちらが正しいか決められない。
His opinion and mine are evenly matched; we can't decide which is right.