Arabic nouns have endings to indicate their grammatical function in a sentence, similar to how we change our clothes based on the occasion. There are three noun endings: dammah, fatah, and kasrah. Dammah indicates the nominative case and subject. Fatah indicates the accusative case and object. Kasrah indicates the genitive case and comes after prepositions, adverbs, or to show possession. Memorizing the Arabic terms for these cases is important for understanding noun functions in Arabic sentences.