"I am the second one."
Translation:Ich bin die Zweite.
I'd like to offer an explanation to new learners of why this is the case, knowing how much it used to confuse me.
The reason is that German articles and adjectives need endings and these endings depend on the gender of the noun that they are attached to. But sometimes when the context is clear, you can leave away the noun. The article/adjective still needs to match to the implied noun, though. In fact, the adjective is actually supposed to be turned into a noun ('nominalised'), which means it gets a capital letter.
In Duo's example, the context is not clear, so we are left with several plausible possibilities:
Ich bin die zweite Person/Frau --> Ich bin die Zweite
Ich bin der zweite Mann --> Ich bin der Zweite
Ich bin das zweite Mädchen --> Ich bin das Zweite
In practice it would be most common for you to choose der/die based on your own gender.
I've written "Ich bin Zweiter". The "-er" end fits here because I've omitted the article "der"?
tank'yu panik102! Even though I'm not learning english, it's always good to find out our own mistakes.
There is another exercise that has "You are the first ones." with eight German words printed below from which to select the desired translation. "Ihr seid die ersten." is the answer that is expected. There is no option to select "Ersten" unless the translation is switched to keyboard and "Ersten" is typed. az_p mentions (above, below, somewhere in this list...) that adjectives used as nouns should have capital letters. Small detail, perhaps, but it would be helpful to have clarification of the inconsistency.
That doesn't really apply to this sentence. Here we have die Zweite ("the second one", which is singular) rather than die zwei ("these two", which is plural). If you wanted to say "the second ones" (i.e. plural) you would need die Zweiten.
As a translation of the English sentence, yes.
You put in a word hier which is not part of the English sentence.
We just don't say that.
Much like in English, we don't say "I am the second us."
English needs a dummy noun "one" where German just uses an adjective.
Ich bin die zweite Eins would mean "I am the second 1" (i.e. there are several 1's, several instances of the number "one", and you are the second of those 1's).
I've answered this twice now, first time with a capital 'Z', second [zweite!] time with a lower case 'z', just as a test. Both were marked correct. I would have thought the capital was necessary, because omitting a specific word to translate the noun 'one' means that Zweite changes from adjective to noun, in which case it takes a capital. But it looks as if it can retain its adjectival role, and lower case initial, even when the noun is only implied.