Learn Arabic (Modern Standard): القرار رسمي.

In Arabic, the subject of a nominal sentence (a sentence without a verb) is in the nominative case. Because القرار (the decision) has "al-" (the) at the beginning, it is definite, so it takes a single Damma at the end, making it القرارُ (al-qaraaru).

Why does the predicate رسمي take a double Damma (tanween) instead of one?

The word رسمي (official) is the predicate, which gives us information about the subject. Predicates are also in the nominative case. Since it does not have "al-" (the), it is indefinite and takes a double Damma (tanween), pronounced as "un". It is read as رسميٌّ (rasmiyyun).

Where is the word for "is" in this sentence?

Arabic does not use a present-tense word for "is" or "are". When you place a definite noun like القرار right before an indefinite adjective like رسمي, it automatically forms a complete sentence meaning "The decision is official."

How do I pronounce the ending of رسمي with its case ending?

The word رسمي ends with a "yaa" that has a shadda, meaning the "y" sound is doubled (rasmiyy). When you add the double Damma (un) for the nominative case, it becomes "rasmiyyun". Make sure to hold that "y" sound slightly before saying the "un".