"This apple is bad."

Translation: Dieser Apfel ist schlecht.

[bpromas]

Why is it "dieser" and not "diese"?

[qbufm07]

This is considered a demonstrative pronoun. When using "diese" in front of a noun, it takes on the ending that is associated with case (masculine, feminine, neuter). If the noun in front is masculine, it ends in ('-er or dieser), if it is feminine or plural, it ends in (-e or diese), if it is neuter, it ends in (-es or diese). Since "Apfel" is masculine (der Apfel), it will be dieser, not diese.

[AutumnAngels]

Thank you !!!! Finally an explanation I can understand.

[JJ1856]

Why not 'Das Apfel'. We've been using 'das' for 'this' in plenty of exercises before. I know that 'das' means 'that', but Duo has been accepting das=this previously.

[Alf-Sawman]

If you use 'Das' directly in front of a noun, it will take the role of the definite article (der/die/das) whereas if you place it in front of the verb it can be an demonstrative pronoun (like this/that in English). In the case that you are using an article, it must follow the gender of the noun, hence you could say either of these:

1 Der Apfel ist verdorben. (Apfel os masculine, hence 'der' for the subject, which takes the nominative case)
2 Das ist ein verdorbener Apfel. (Here 'das' is a demonstrative pronoun.)

:-)

[armeezy]

Another question: it suggests "Der Apfel" to me, why is that?