What does german word Der mean?

"Der" is a German definite article, meaning "the". It's used before masculine nouns in the nominative case.

Here are some examples:

* Der Mann (The man)

* Der Hund (The dog)

* Der Apfel (The apple)

It's important to note that German has three definite articles, depending on the gender of the noun:

* Der (masculine)

* Die (feminine)

* Das (neuter)