# When would I use ふん instead of ぷん?

What's the difference for using these?

Examples:

さんじごじゅうぷん

ろくじよんじゅうごふん

• You might want to recheck your textbook or other source from which you got these - your first example should probably be さんじごじっぷん or さんじごじゅっぷん (not じゅうぷん). Anyway, the answer to your question involves a phenomenon called rendaku (連濁), sometimes translated as "sequential voicing". This answer has a good overview of the phenomenon. – senshin Jan 12 '15 at 5:40
• This is similar to the difference in the English phrases an apple and a tomato. (as in, there's no difference in meaning) – blutorange Jan 12 '15 at 17:17
• I don't think /h/ → /p/ is the same thing as rendaku. It's explained by a separate rule. – snailplane Jan 13 '15 at 15:05

It all depends on the numbers immediately preceding 「分」.

ん Hun」: 2, 5, 7, 9 and 00.

ん Pun」: 1, 3, 4, 6, 8, 10, 20, 30, 40, 50, etc.

Examples:

ん Hun」： 32分（さんじゅうにふん）、15分（じゅうごふん）、57分（ごじゅうななふん）、9分（きゅうふん）、4-5分（しごふん [Only number 5, not number 4, affects the way 分 is pronounced.]）

ん Pun」： 1分（いっぷん）、13分（じゅうさんぷん）、24分（にじゅうよんぷん）、6分（ろっぷん）、20分（にじゅっぷん）、60分（ろくじゅっぷん）、2-3分（にさんぷん）

「0分」 can be read both 「ゼロふん」 and 「れいふん」.