The file extension for native Microsoft Word documents is ".doc".

Explanation:
Microsoft Word is a popular word processing software developed by Microsoft. It is widely used for creating, editing, and formatting text documents. When you save a document in Microsoft Word, it is saved with a file extension that represents the file format.

The file extension for native Microsoft Word documents is ".doc". This extension stands for "document" and is used to indicate that the file is a Word document. It is the default file format used by older versions of Microsoft Word, such as Word 97-2003.

Key Points:
- Microsoft Word is a word processing software developed by Microsoft.
- The file extension for native Microsoft Word documents is ".doc".
- The ".doc" extension stands for "document" and indicates that the file is a Word document.
- It is the default file format used by older versions of Microsoft Word, such as Word 97-2003.

Additional Information:
In newer versions of Microsoft Word, such as Word 2007 and onwards, the default file format has changed to ".docx". The ".docx" extension stands for "document file (Open XML)" and is based on XML (eXtensible Markup Language). It is an open standard file format introduced by Microsoft to improve file compatibility, reduce file size, and enhance security features.

In conclusion, the file extension for native Microsoft Word documents is ".doc". This extension represents the default file format used by older versions of Microsoft Word. However, it is important to note that newer versions of Microsoft Word use the ".docx" extension as the default file format.