This was originally a two-part post on cohost.

One thing that bothers me about bopomofo is that words ending in ㄛ get an extra vowel ㄨ (essentially just /w/) in the middle sometimes when spoken but it’s never written down. Specifically the following:

• ㄅㄛ /bwo/ (e.g. 伯)
• ㄆㄛ /pwo/ (e.g. 婆)
• ㄇㄛ /mwo/ (e.g. 魔)

But any other word ending in /wo/ has to be written as ㄨㄛ, which makes far more sense: ㄨ is the u that turns into semivowel w and ㄛ is the o. It’s inconsistent that it’s not written ㄅㄨㄛ、ㄆㄨㄛ、ㄇㄨㄛ, and it trips me up because my keyboard doesn’t accept those as alternatives even though that’s how they’re pronounced! I don’t think it’s a dialectical thing either, because bopomofo is used basically exclusively in Taiwan, so it would only be for Taiwanese Mandarin anyway.

Another thing that bothers me about bopomofo is that there’s no separate vowels for -eng and -ong (idk what the IPAs are so I’ll leave it at that). For most initial consonants you would use -ㄥ for the former and -ㄨㄥ for the latter: these are ㄉ、ㄊ、ㄋ、ㄌ、ㄍ、ㄎ、ㄏ、ㄓ、ㄔ、ㄕ、ㄖ、ㄗ、ㄘ、ㄙ. For ㄐ、ㄑ、ㄒ you can’t end in -eng, and to end in -ong you’d use -ㄨㄥ.

For ㄅ、ㄆ、ㄇ、ㄈ it’s a little more complicated. In Taiwanese Mandarin, *beng, *meng, and *feng don’t exist¹, so bong, mong, and fong are written as ㄅㄥ、ㄇㄥ、ㄈㄥ despite the fact that it would be more consistent to stay with -ㄨㄥ.

However, there are both peng and pong but they’re both written ㄆㄥ, not ㄆㄨㄥ for the latter! It makes no sense! For instance, 朋、棚 are pronounced péng, while 捧 and 碰 are pronounced pǒng and pòng. (I don’t know if there’s a word pronounced pōng.) I very much would never, ever rhyme 朋 and 碰, and yet there is only one way to spell it phonetically.

Maybe whoever invented bopomofo simply never accounted for these variations. I just think the obvious answer was there all along (using -ㄨㄥ as needed) and I’m annoyed the rules — and more importantly, my phone keyboard! — don’t even allow this combination.