What does the use of a dash (instead of a character) to extend a sound mean?


I came across the sentence `混乱する気持ちもよーくわかる` in my manga. I have translated it,
but the use of the dash (which was vertical in the actual vertical text)
stumped me for a bit (I thought it was よう at first, not よお). I was under the
impression that a dash like that is only used in katakana, and in hirigana
they use the character of the sound they want to extend. But that's not the
case here.

So what does it mean when this happens? Is is a special case or exception, or
is there some rule?

By the way, I ended up with `よーくわかる` all together meaning "I know you..."
(thanks, Google Translate, for being more useful than a dictionary for once),
which seems to be right in this context (In this case, "I know you're feeling
confused"). That's why I think it might be a special case. (Searching よお on
it's own ended up with "trouble brought on by sins of forebears"...)




In Katakana, we use ー for some long vowels indeed. But words with it, like ユーロ
are spelt this way!

However, in your case, there is no such word よーく、 ようく nor よおく. What this dash
means is that the _sound_ is lengthened. The word is just "よく". So, when the
author wrote "よーくわかる" he meant "I reaaaaally understand".

That's it!




In Katakana, we use ー for some long vowels indeed. But words with it, like ユーロ
are spelt this way!

However, in your case, there is no such word よーく、 ようく nor よおく. What this dash
means is that the _sound_ is lengthened. The word is just "よく". So, when the
author wrote "よーくわかる" he meant "I reaaaaally understand".

That's it!

