A case marker is a linguistic element that indicates the grammatical function of a noun or pronoun in a sentence. It helps clarify the role of the word, such as whether it is the subject, object, or shows possession. Case markers are often found in languages with rich inflectional systems, like Latin or Russian, where they change the form of the word. In some languages, case markers are added as prefixes or suffixes to nouns. For example, in Japanese, particles like "が" (ga) and "を" (wo) serve as case markers to denote the subject and object, respectively. This system aids in understanding sentence structure and meaning.