Im Deutschen/ins Deutsche/auf Deutsch/das Deutsch/das Deutsche.
I should like to know more about the word Deutsch(-) in the aforementioned phrases. The impression I have is that there is the noun 'das Deutsch' (used in the phrase 'auf Deutsch' or in the clause 'Ich kann Deutsch'), but there is also the substantivised adjective 'das Deutsche' (used in the phrases 'ins Deutsche' and 'im Deutschen'). Is that correct or am I just making up things? And if it's correct, do all of them have the exact same meaning? It just seems weird that you'd need a substantivised adjective if you already have a noun that means exactly the same thing.
Thanks in advance.
Deutsch/Deutsch has a lot of meanings, depending in the exact use, but they all have something to do with Germany (who would have thought^^):
Das Deutsche (The German language), also die deutsche Sprache Im Deutschen -> in German, as in 'In German we capitalize nouns' auf Deutsch -> also in German, but rather used in this sentence: 'What is glove in German?' Das Deutsch -> rarely used with article, rather like you did correctly in your example 'ich kann Deutsch' (although I am not sure that would be capitalized)
They all mean the same thing, and you can use them, but some are more common in certain phrases than others.
Also, to complete your list: Der/Die Deutsche -> The German (male/female)
Noun is 'das Deutsch' AND "das Deutsche" (there are 2 forms for the same thing, they have slightly different inflections). Both are neutrum singular nominative, some words have 2 forms. Neither me or the normal dictionary can tell me the reason how those 2 forms were created, so I dont think of a substantivised adjective, its a normal word for me (both forms are normal).
This might be weird, but you got how it is.
Just a quick follow up: I checked Duden and it gives three important entries:
http://www.duden.de/rechtschreibung/deutsch - deutsch, Adjektiv - 2a. Großgeschrieben wird das substantivierte Adjektiv, wenn es im Sinne von »deutsche Sprache« verwendet wird.
http://www.duden.de/rechtschreibung/Deutsche_Sprache - das Deutsche, substantiviertes Adjektiv - Die deutsche Sprache im Allgemeinen.
http://www.duden.de/rechtschreibung/Deutsch - das Deutsch, Substantiv - die deutsche Sprache [eines Einzelnen oder einer Gruppe]; die näher gekennzeichnete deutsche Sprache.
That's slightly insane, but okay, I'll just have to deal with it. :P The only question that remains for me is whether e.g. 'auf Deutsch' falls into the 1st or 3rd case, since Duden gives 'etwas auf Deutsch sagen' as example for both the 1st and the 3rd entries... I really don't understand how it can be an adjective if it's not at all inflected. Not that important to know, but I was just curious anyway. :P Thnks for all the replies.