Noun cases are grammatical categories that indicate the role a noun plays in a sentence. Different languages use noun cases to show whether a noun is the subject, object, or shows possession. For example, in English, we primarily use word order, while languages like Latin or Russian have specific endings for nouns to convey their function. There are several common noun cases, including the nominative (subject), accusative (direct object), genitive (possession), and dative (indirect object). Each case helps clarify the relationship between nouns and other words in a sentence, making communication clearer and more precise.