Translation:Bread is food.
When there was a sentence asking to write "A book is a thing/Books are things" (책이 물건입니다, according to Duolingo...), it did not accept the particle "은". It seems to me that this sentence here (about the bread) is very similar grammatically to the other one. So... what is the explanation for using 은/는 and 이/가 in this context?
It matter Coz you can't speak with everyone by the same way For example you use the low inforamal for you friends or younger ppl and so on by adding (어) and with older and strangers you use the low formal by adding (어요 ) amd in this case 예요 and lastly the HIGH FORMAL am not sure with who do you use this but i think its usually used when you want to show more respect and i hear for example you can use this with your principal and so .. As i said am not ver sure abt it Hope i was helpful Don't forget i love hoseok