In English, ¨ is a diacritic mark called diaeresis, which indicates that a vowel is distinct, and shouldn't be diphthongized or dropped: Coöperation, Noël, Brontë.
In German, ¨ is a diacritic mark called umlaut, which transforms the vowels A, O, and U into their umlauted versions: Ä, Ö, and Ü. These characters are not distinct letters of the German alphabet, but belong to a special weird in-between class.
In Swedish, ¨ is not a diacritic mark, does not have a name, and is simply an integral part of the letters Ä and Ö, which together with Å are distinct letters of the Swedish alphabet. The dots aren't modifiers, they're not optional, Ä is not sort-of-an-A, it's as distinct from A as any other vowel, and its pronunciation is closer to E than A.
I had a german teacher insist we write umlauts as two little dashes instead of dots, because "they're not trémas" (French for diaeresis) which are written as two little dots. The wikipedia article above seems to say they're the same. Was I lied to all these years ?
To me, in Swedish, Ā and Ä and an A with two small dashes above would be the same letter, but with stylistic typeface differences. It doesn't change the letter itself. I have never heard of any German insisting their umlauts shouldn't be dots, so I think your German teacher was just a bit pedantic/insane.
Conceptually umlaut dots are different from trema dots, but who cares?
That's pretty funny - makes me think it's less diaeresis (thanks! TIL) and more akin to the dot over a lower case i or j: A letter with distinct sounds that can't be written without the marking above it.
Yes, that's actually a great example! The dot over i doesn't have a name and isn't a diacritic mark any longer, it's an integral part of the letter. It probably originated as a diacritic mark, though.
Ä in Swedish originated as the AE ligature where the E moved upwards and above the A until it became stylized as two dots. In Danish and Norwegian, they instead promoted Æ to a distinct letter.
I think the OP is splitting hairs. I'd say that they are just as much different letters in German, from which the word "Umlaut" comes.
One is replaced with the other in word inflections. For instance, the noun "Land" is "Länder" in plural — both in German and Swedish.
But what the two dots are not: they are definitely not diaeresis.
You don't think of "y" being "u" with an Umlaut. For you this is a completely seperate letter. Ditto with ÄÖÅ im Swedish and ÆØÅ in Danish (Æ is never thought of as combined A and E).
Only in languages where they are umlauts. Look at, for example, Ä and Umlaut-A: they have historically been written differently. They were simplified to mean the same thing in handwriting a long time ago, but as recently as in iso-8859-1 they made a conscious decision to merge them.
Unicode also makes a difference, but generally recommends the merged character.
In English, ¨ is a diacritic mark called diaeresis, which indicates that a vowel is distinct, and shouldn't be diphthongized or dropped: Coöperation, Noël, Brontë.
In German, ¨ is a diacritic mark called umlaut, which transforms the vowels A, O, and U into their umlauted versions: Ä, Ö, and Ü. These characters are not distinct letters of the German alphabet, but belong to a special weird in-between class.
In Swedish, ¨ is not a diacritic mark, does not have a name, and is simply an integral part of the letters Ä and Ö, which together with Å are distinct letters of the Swedish alphabet. The dots aren't modifiers, they're not optional, Ä is not sort-of-an-A, it's as distinct from A as any other vowel, and its pronunciation is closer to E than A.