"The boys drink my wine."
Translation:Die Jungen trinken meinen Wein.
Wein is a masc noun. I may be wrong on this but when something is happening to a masc. noun it goes from mein to meinen. So if I were to just say "My Wine" it would be "mein wein". If I were to say "I am drinking my wine" it would be "ich trinke meinen wein". Same as the difference in Der wein vs Den wein.
As in the dictionary it is der Wein. A masculine noun. In this sentence it is in the accusitive case. What are the boys drinking: "My wine". Think of it as some one is pointing a finger at you "accusitive". In the acc. case mein now receives "en". Meine is feminine so it would go with the gender die. In the accusitive case the ending of Mein would receive "e" or Meine