In a Windows OS, what is the default file extension for a Word document?

The default file extension for a Word document in the Windows operating system is .docx. This format was introduced with Microsoft Word 2007 and has since become the standard format for saving Word documents. The .docx extension is part of the Office Open XML standard and is designed to offer improved data management and better support for features such as formatting and complex document structures.

The .doc extension is associated with earlier versions of Microsoft Word (prior to 2007) and is not the default for current editions. The .txt extension represents a plain text file, which does not support rich formatting typically found in Word documents. The .wps extension is linked to Microsoft Works documents, which are not commonly used in the current context of Microsoft Word applications. Therefore, .docx is the correct and up-to-date choice for Word documents in a Windows environment.