"Invalid (Unacceptable)" refers to something that is not valid or does not meet established standards or criteria. This term is often used in various contexts, such as legal documents, computer systems, or social norms, to indicate that a particular action, request, or item is not recognized or permissible. In legal terms, an invalid contract may lack essential elements like consent or consideration, rendering it unenforceable. In technology, an invalid input in a software application may trigger an error message, indicating that the data provided does not conform to expected formats or values, such as email addresses or passwords.