Pronunciation of "何" as "なん" or "なに"

Question

"何" is pronounced as "なん" before counter-words like in "何時{なんじ}", "何歳{なんさい}" etc; or before particles like in "何で", "何とか" etc.

However, it remains to be pronounced as "なに" in some words like "何事{なにごと}", "何色{なにいろ}", "何者{なにもの}" etc. It can also be pronounced both ways like in "何か".

What is the logic/origin behind this pronunciation difference?

Answer 1

This isn't a complete answer, but there is a strong tendency to shorten to なん when 何 is followed by a 'n', 'd' or 't' sound.

This obviously doesn't address your first two examples, however.

Answer 2

Usually we use "なん" in the following cases :

• when the first syllabe of the next word is part of the lines "-た", "-だ" and "-な",
• as mentioned by Luckman, when we ask a question about a number like in "何時{なんじ}" and "何分{なんぷん}".

In any others cases, we use "なに".