"My child is playing."
Translation:Mein Kind spielt.
I understand now. I was doing this lesson while tired and thought it said "My child is not playing" so I typed "Mein Kind spielt nicht" and it told me that I used the er/sie/es form when I should be using the sie/Sie form which was what confused me. Once I took out the nicht, however, everything was good.
They do, but what is "My child/Mein Kind" in this sentence? The subject in nominative case. "Kind" is neuter and singular ("das Kind"). The neuter nominative singular declination of "mein" is "mein."
Say, you had the sentence "Ich bin der Vater meines Kindes." - I am the father of my child. Here, "meines Kindes" is in genitive case. Hence, the neuter genitive singular declination of "mein" is "meines."