"He drinks this wine."
Translation:Er trinkt diesen Wein.
diese is for nominative and accusative of feminine noun, diesen is for accusative of masculine. The chart for remembering
Case: maskulin – neutral – feminin – Plural
Nominativ: dieser – dieses – diese – diese
Akkusativ: diesen – dieses – diese – diese
Dativ: diesem – diesem – dieser – dieser
Genitiv: dieses – dieses – dieser – dieser
Or use this shorter chart
maskulin – neutral – feminin – Plural
Nominativ: r – s – e – e
Akkusativ: n – s – e – e
Dativ: m – m – r –r
Genitiv: s – s – r – r
You might think of words like 'dative' and 'accusative' as meaning 'indirect-' and 'direct-object'.
'Nominative' as 'subject'. 'Genitive' as 'possessive'. It gets weird when prepositions enter the picture, but in the beginning this will help you to make sense of most of the linguistic jargon people toss around.
This question is actually answered all the time in many other threads (and by this point we all should have seen them multiple times). Here's the short version:
Nominative = the subject of the sentence (The boy gives the apple to the girl)
Accusative = the direct object (The boy gives the apple to the girl)
Dative = the indirect object (The boy gives the apple to the girl)
Genitive can most easily be described in English as the "possessive" case (The boy's apple or The apple of the boy).
So for example with (The boy gives the apple to the girl) the boy = der Junge (nominative masculine), the apple = den Apfel (accusative masculine), and the girl would be dem Mädchen (dative neuter).
The problem is it mostly does come down to memorization. There are etymological reasons for why some case changes end in "n" and some in "s" and others in "r", etc. but it's not necessarily strictly "logical".
This is just how language works and morphs over time and there's no short three sentence summary for hundreds of years of history. Even these charts are just the base starting point because, like with any language, there are the rules and then there are the exceptions to those rules which can only really be learned by memory.
It's funny that people speaking English go crazy about all these cases)) I can imagine how awful this system of endings looks) in Russian language, we have even 2 more cases, so german is quite ok for us)))) I have learnt german for several years now, but after any pause I forget everything... God give me some memory!