Is Vokabular der, die or das?

The correct German article for Vokabular is das. The noun Vokabular is Neuter. So you always say: das Vokabular. Learn the article together with the noun — German nouns don't follow predictable gender rules most of the time.

The plural of Vokabular is: die Vokabulare. In the plural, every German noun takes the article "die". So: die Vokabulare. Example: ein Vokabular → zwei Vokabulare.

Correct: die Vokabulare. The form "die Vokabulars" is wrong. The plural of das Vokabular is die Vokabulare. In the nominative plural, you always use the article "die".

das Vokabular follows the four German cases. Nominative: das Vokabular, Accusative: das Vokabular, Dative: dem Vokabular, Genitive: des Vokabulars. In plural: die Vokabulare / den Vokabularen. Learn these forms together with the noun.

The genitive singular of das Vokabular is: des Vokabulars. The genitive plural is die Vokabulare. German uses the genitive to express possession or belonging. Example: die Farbe des Vokabulars.

The dative plural of Vokabular is: den Vokabularen. In German, dative plural nouns usually end in "-n". So you say: "mit den Vokabularen". Use this case after prepositions like mit, von, bei, zu.

Vokabular is a noun and must be capitalized in German. You'll find example sentences above for each case. The article das stays the same in nominative singular but changes in other cases. Practice declension in your own sentences.

Yes, Vokabular is a noun (also called a substantive). German nouns are always capitalized. The article for Vokabular is das. Every German noun has a fixed article you must memorize.