Completely out of context, if you say "Ele escreveu uma composição" here in Brazil I believe most people will think you are talking about a song, "he wrote a song", but I don't think that would be the understanding of most people when you say "He wrote an essay", I guess most people will think of a text, like in an article or short paper...
Hence, I think a better translation for "He wrote an essay" would be "Ele escreveu um artigo", and a better translation for "Ele escreveu uma composição" would be "He wrote a song".
Thanks. Just the question I was coming to ask.
The english is somewhat vague. I don't think English speakers would say "He wrote a composition" to describe the creation of a musical piece unless it was really clear from the context what type of composition he wrote. We'd say "He wrote a song/symphony/samba" or use the word "compose" as a verb- "He composed a song/samba/sonata".
One of the hover hints given for "composição" is "conciliation," which is, of course, not correct. Here is what I think happened:
One meaning of "composição" is "composition" as in "chemical composition." Another word for that sense of "composition" is "makeup." But there is also the verb "make up," as in, "After we fight, we always make up." And "conciliation" is the the action of making up with someone. By this five-link chain of word association,
composição --> composition --> makeup --> make up --> conciliation
"conciliation" was entered as a hint for "composição." I guess it could as easily have ended up as "cosmetics."
That is my guess. I wonder what process Duolingo has for creating hints that makes such as thing possible.