"It is a man."
Translation:Es ist ein Mann.
Thank you. (i had the same question as Nel91) Could you tell me why 'It' can't be the subject. I translated 'It is a man' into 'Es ist einen Mann.' You say that there is no fixed sentence structure, but then why can't Es be the subject? OR, is there something obvious about this sentence that makes Mann the subject? (I'm as new as you can be to German--so feel free to explain 'the obvious.') :)
EDIT: I just read bellow to Levi's comment. The state of being a man describes 'it' and doesn't take action from it. Is that why 'it' (es) isn't the subject? Just repeating what I wrote, I'm confusing the nominative with being the subject. Any clarification would be helpful.
More than that. Because that verb is reflexive, it takes no object. In a sense, both sides are subject. You should be able to reverse the order and still made sense. Thus, all adjectives, articles, etc. associated with nouns bridged by "to be" take the gender-matched nominative form.
You're right, the sentence "It is a man" doesn't really make sense in german. The only translation I could imagine would be "Das ist ein Mann". But that would be in english "this is a man". So even your translation "Er ist ein Mann" does actually belong to the sentence "he is a man".
This is clearly only an exercise of direct translation and a example of nominative/nominative case use. For proper understanding I would recommend not to try to put every phrase here in a specific context whatsoever. Just translate the phrase. Not every sentence in Duolingo would make sense in casual daily conversation at all.
There is a simple rule in English and in German: "The verb 'to be' never takes an object". In other words, "I am / you are/ he, she, it is / we are / you are / they are" and "ich bin / du bist / er, sie, es ist / wir sind / ihr seid / sie sind" are always followed by a nominative case (ein Mann) and never followed by an accusative case (einen Mann). Don't ask why. That's just how it is! Languages are not always logical!