one tenth; one hundredth; one percent; one tenth of a sun; one quarter ryō (an old coin)
「１分」 has another reading with different meanings.
one minute
一分の隙なく完璧だ。
It is perfectly flawless.
彼の発言に一分の誤りもない。
There is not a single error in his statement.
その仕事はまだ一分しかできていない。
That work is still only one-tenth done.