Why isn't "They know my dog" accepted here? I know Sie is capitalized, but it's at the beginning of the sentence so I thought it was ambiguous.
Could be formal you, and could be plural too, as in You guys know my dog?
It cannot be plural. If it was plural, it would have to be: Ihr kennt meinen Hund.
I'm no native speaker, but I believe that formal-plural-you would also be 'Sie kennen'.
"Sie kennen" is the formal "you" conjugation, but as quis_lib_duo said above, "they know my dog" should also be accepted here. A capitalized "Sie" is an indicator of the formal "you," since it would not be capitalized for "they." However, here "Sie" is at the beginning of the sentence, making it ambiguous since "Sie" would need to be capitalized in either scenario.
Until here,I didn't see an acceptable answer for the comments.please explain how we can translate (Sie) to (you). Thank you if you answer very soon.
First comments I've lookes at. Still confused at wheb it's she ans it's they, but this is a confusing translation!
So we would pretty much have to rely on context to determine if Sie meant you or they.
When you hear someone else speak, you can determine the person from the verb as well.
Sie kennen - they know
Sie kennt - she knows
When you speak, well you know who you're speaking too.
The verb 'kennen' requires us to use the accusative case, and just like in English, that the pronoun 'he' changes its case and becomes 'him' in the sentence: "They know him", in German, nouns change their article (in this case a possessive article) from 'mein' to 'meinen'.
In this case (Akkusativ) only the male nouns change.