Breakdown of Der Schüler schreibt einen langen Aufsatz über rote Blumen.
lang
long
die Blume
the flower
schreiben
to write
einen
a
Questions & Answers about Der Schüler schreibt einen langen Aufsatz über rote Blumen.
What case is der Schüler in, and how can I tell?
der Schüler is in the nominative case. You know because it’s the subject of the sentence (the one doing the action), and nominative is always used for subjects. The article der is the nominative masculine singular form.
Why is it einen langern Aufsatz?
Because Aufsatz is masculine (der Aufsatz) and here it’s a direct object, so it takes the accusative case. The masculine accusative indefinite article is einen. The adjective lang gets the weak ending -en in accusative masculine after an article (einen → langen).
Why does lang become langen in langen Aufsatz?
German adjectives change ending according to gender, case and whether there’s an article. After an indefinite article in masculine accusative, adjectives take the weak ending -en. So lang → langen.
Why is there no article before rote Blumen?
There is no indefinite article in plural (like English “some”), so you either use a definite article (die roten Blumen) or no article (rote Blumen) when speaking about flowers in general or unspecified ones. Here the phrase is indefinite plural, so the article is omitted.