Case marking is a grammatical feature that indicates the role of a noun or pronoun in a sentence. It helps clarify whether a word is acting as the subject, object, or showing possession. Different languages use various methods for case marking, such as inflections, prepositions, or word order. In languages like Latin or Russian, case marking is often achieved through changes in the endings of words. For example, a noun may have different forms depending on whether it is the subject or the object of a verb. This system aids in understanding the relationships between words in a sentence.