"This is my lamp."
Translation:Das ist meine Lampe.
There is an a e missing in the last word (Lampe). More importantly, you translated a slightly different English sentence:
"This is my lamp." = "Das/Dies ist meine Lampe."
"This one is my lamp." = "Diese ist meine Lampe."
The second English sentence is a bit unusual and would require an appropriate context. The same is true for the German translation.
When translating "This is my lamp" you have a choice between dies and das because das, while formally and etymologically corresponding to that, has actually become a more general demonstrative pronoun that can be used both for this and for that. Often in English it doesn't really matter whether you choose this or that. There doesn't seem to be anything wrong with "To be or not to be, this is the question" other than that it's not how Shakespeare wrote it. In those situations, German normally uses das. However, the original meaning of das is still present when you contrast it with dies, as in the idiomatic expression dies und das (this and that).
QUOTE: 'I wrote: "Diese ist meine Lampe"; why is it incorrect? Diese is for feminine right?'
Diese is for feminine when it is an adjective, not a pronoun. The "this" in "this door is closed" and "this is a door" are different. The first one acts as an adjective and the second acts as a pronoun
It can be this or that, either one; you translate by context.
Also, when 'das', 'dies' and 'jenes' are used with forms of 'sein' (the verb to be), they can refer to singular and plural nouns of any gender:
Das ist meine Lampe. Dies ist mein Mann. Das sind meine Kinder.
Otherwise they match gender and case: Dieser Mann.
(Note that in these sentences, the nouns are also nominative, another interesting feature of 'sein'. That's because subject and object are the same thing -- equivalent. So NOT "Dies ist meinen Mann" because Mann is nominative, not accusative.)
I wonder why I can't say "Die ist meine Lampe". I'm sure I've heard that. At least one source seems to say that I can. http://www.germanlanguageguide.com/german/grammar/demonstrative-pronoun.asp
Your proposed sentence is a bit unusual even in colloquial speech. Your source doesn't actually say you can say that. I guess the fact that das can be either a demonstrative pronoun (that) or a definite article (the, for neutral nouns) in connection with the tables in the source caused some confusion. (Or maybe it happened because your source says that demonstrative pronouns can be used like definite articles - in confusing words that seem to imply that definite articles can also be used like demonstrative pronouns, which is not generally true.)
- "This is my lamp" = "Dies/das ist meine Lampe". ("Dies" if you really insist on this as opposed to that. "Das" is the generic demonstrative pronoun to be used when you don't care about the difference between this and that.)
- "This one [thing] is my lamp" = "Dieses ist meine Lampe."
- "This one [lamp] is my lamp" = "Diese ist meine Lampe."
- "It [= the thing] is my lamp" = "Es ist meine Lampe."
- "It [= the lamp, literally she] is my lamp" = "Sie ist meine Lampe."
Note how in German you can't avoid indicating whether with this one or it you are referring to some generic object (neutral) or to a lamp in particular (female).
"Diese[s] ist meine Lampe" sounds a bit stilted. Due to the clash between grammatical gender of a lamp (female) and natural gender (neutral), most people would prefer "Dieses ist meine Lampe". However, as this would only be used in somewhat elevated speech where silly genders can be considered a feature rather than a bug, all bets are off.
"Es ist meine Lampe" is perfectly normal German. "Sie ist meine Lampe" is grammatical but sounds almost as weird as "She is my lamp" would sound in English. (Don't ask me why, but maybe someone else knows.)
Finally, in colloquial German you can replace the personal pronouns er, sie, es by the definite articles der, die, das. If you do this in an essay in a German school, it will be marked wrong, but it's what people actually say most of the time. So we can add two more options:
- "It [= the thing, colloquial] is my lamp" = "Das ist meine Lampe."
- "It [= the lamp, literally she, colloquial] is my lamp" = "Die ist meine Lampe."
The first of these is indistinguishable from one of the two variants of our very first option. So it's not clear whether "das" means this/that or it.
The last option is what you proposed. Even though it's just the colloquial variant of "Sie ist meine Lampe", it sounds much less weird. (Maybe due to the similarity between "die" and "dies"? Does someone know?) I can imagine saying this under certain circumstances, although I would be much more likely to say "Das ist meine Lampe". "Die ist meine Lampe" requires that the object has already been firmly established as a lamp (or another grammatically female object).
Summary: It's a correct translation of "It is my lamp" into colloquial German. There are two and a half reasons for Duolingo to reject it. (1) Because it's colloquial. (2) Because it translates a slightly different sentence, though one with essentially the same meaning. (3) It has a female pronoun where usually a neutral one would be preferred, especially when there is no further context.