Is Abo der, die or das?

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

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

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

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

The genitive singular of das Abo is: des Abos. The genitive plural is der Abos. German uses the genitive to express possession or belonging. Example: die Farbe des Abos.

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

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