"친구는 공이 있습니다."
Translation:A friend has the ball.
It depends on how you look at it. Some languages say a ball is with or on the friend to mean that the friend has a ball. "A friend" is the topic, so it is like saying "As for the friend, there is a ball (with him)." only don't use that for an answer as that is just an idea of how the emphasis might work. They want us to translate the common Korean way of talking to the common English way of talking.
This is the topic marker, which shows what the speaker is talking about. The topic is singled out as if you said “Regarding” or “As for” the friend, (he or she) has the ball.
This sounds like it was written from the perspective of a pup: defining a friend as someone who has the ball.. Or, is the phrase idiomatic? Kind of like saying 'the ball is in your court' in English..?
This is not a definition. The friend has a topic marker, so it is more like “As for the friend, the ball is located (with him) which is translated to the common “The friend has the ball.” This is simply how they indicate location of items and ownership of items. The owner has the topic marker and the item has the subject marker if a location is given there is a marker for that as well. https://www.duolingo.com/skill/ko/basics-2/tips-and-notes
This is “As for the friend, the ball is located there (with him).” which is how they indicate location and ownership of items and it is translated to the more common English expression “The friend has the ball.” See below for more information.
Why "the ball"? I am not understand this. This should be a friend have a ball instead