Grammatical case refers to the role a word plays in the structure of a sentence, such as the subject of the clause or object of the verb. Some languages change the form of a word (inflect) to indicate case, while other languages rely on word order. It is important to understand the difference between part of speech (nouns, verbs, etc.) and case (subject, object, etc.) because these are the foundation of syntax. Understanding the meaning of sentences and larger texts depends on understanding case.