I need help analyzing the phrase 発音上の

Question

I’ve been reading about sound change in Japanese and I keep coming across the phrase ‘発音上の’ as in

発音上の相違に支えられて開合の仮名遣いに区別がありました.

In the above example, what purpose does ‘上’ serve? Should I read ‘発音上’ or 発音‘上の...’？

Answer 1

This is the suffix 上【じょう】:

じょう 【上】

[一] ...

[二] （接尾）
名詞に付いて、…に関して、…の面で、…の上でなどの意を表す。 「一身－の都合」 「道義－の責任」 「行きがかり－しかたがない」

Since 発音上 is not a single word and you can identify 発音 as a word from the context, the trick would be to look in a monolingual dictionary for definitions of 上 as a suffix. There are only 上【じょう】 and 上【うえ】 and context tells you it would not be the suffix 上【うえ】 (as in 父上).

Answer 2

It is a suffix pronounced as じょう.
https://dictionary.goo.ne.jp/word/en/上/#je-35203
https://dictionary.goo.ne.jp/jn/107334/meaning/m1u/上/

According to "A Dictionary of Intermediate Japanese Grammar", page 76:

上: a suffix which indicates the idea of "from the viewpoint of", "for the sake of", "for the reason", or "in terms of"

Example:

この映画は教育上よくない。
This film is not good from an educational point of view.