"You know my dog."
Translation:Sie kennen meinen Hund.
"Sie" is also polite/formal you.
So it has three meanings: She, They and You (Formal).
"Sie kennen meinen Hund." I think in this example, the person is talking to a stranger or probably his or her boss so "Sie" was used. Remember that Sie could mean "she", "them" or "you" formal. If you're confused, just look at the verb used here (kennen). Kennen can't be used for "du" coz the verb will be conjugated to "kennst". It can't also be used for 3rd person singular/sie coz the verb will be kennt. Hope it helps
You cannot use kennst if you are using "sie".
Verb: Kennen If you conjugate this verb, it'll be like this:
Singular: Ich kenne (I) Du kennst (You informal) Er/sie/es kennt (he/she/it)
Plural: Wir kennen (We) Ihr kennt (You all) sie/Sie kennen (they/You formal)
Hope it helps
Could be like this?: Du kennst meinen Hund. Someone could explain, so far I do not understand.
When I typed 'du kennst meinen Hund' in, Duo accepted it as correct. I guess it depends if you are talking to a person in a formal way (Sie) or in an informal way (du).
This is also correct if you are talking to someone you know like your friends or family members. But to be more polite, "Sie" was used in the example. Duo said "Sie kennen meinen Hund." This is quite tricky coz it could also mean "she knows my dog" or "they know my dog". If you're having trouble deciding which person was used, just look at the verb. It'll help you decide which pronoun suits the sentence. In this example, "kennen" was used so you have to choose "Sie" formal.
This is an example of Akkusativ case. You are right, Hund is a masculine noun, but take note that since it's in Akkusativ case, mein will become "meinen" coz the direct object here is the Hund.
I put weisst and it counted as wrong. How do you know when to use weissen versus kennen?
'Wissen' is to know a fact or knowledge, and 'kennen' is to know/be acquainted with someone/something, if that helps