"I am a child."
Translation:Jag är ett barn.
It's irregular. All words are either an ett-word or an ett-word and you'll have to learn it by heart. However, about 80% of words are en-words so they are a lot more common.
I translated as: Jag är en barn (wrongly), can we say that we use 'ett' instead of 'en' because child means both boys and girls (masculine and feminine)?
No, there's no real rule to it. Some words are just ett, and "barn" is one of them.
The suggestion told me that "child" is "barn". But the answer is "unge". And I was like..... WHAT?
Barn and unge are fairly interchangeable. If it's marked as incorrect, it's either a glitch, or you had some other error in the sentence. (Like writing "ett unge" or "en barn". It's "en unge" and "ett barn.)
Isn't "en" more suitable for persons? i read that "ett" is more appropriate for objects and not people
Almost all living things are en words in Swedish. Ett barn, ett lejon (a lion) and ett får (a sheep) are the only living things i can think of off the top of my head that are ett words.
Most normal objects are en words too, but if you're doing living things you can just assume that and animals and people are en words except for those three.
As for the objects you just have to learn them by heart, though if you find them in the wild its very easy to tell if a noun is en or ett because there's almost always one more word in the sentence that will give it away.