"Dieser Wein ist gut."
@Duomail: to elaborate a bit further on what christian said. The problem is that you can't easily distinguish between the article 'der' and the demonstrative pronoun 'der' in this sentence. If you see it in written form, you'll normally interpret it as being the article. In spoken German you can put enough emphasis on the 'der' to make clear that you mean the demonstrative pronoun.
Easy, - Dieser = Masculine noun ( der Hund -> Dieser Hund) (the dog -> this dog) - Diese = Feminin noun (die Tasche -> Diese Tasche) (the purse -> this purse) - Dieses = Neutral noun (das Kind -> Dieses Kind) (The kid -> This kid) - Diese = Plural nouns (die Katzen -> Diese Katzen) (The cats -> Those cats) These are demonstrative pronouns
Guide yourself by the endings, R, E, S and E, if it helps you.
Hope this helps, if I'm wrong, let me know bitte :)