The most widespread misconception is that .com is an abbreviation for "company." The error seems logical because private corporations dominate the space. However, Postel and Reynolds designed the namespace around activity types rather than corporate governance structures.
RFC 920 explicitly defined the category: "COM - Commercial, this domain is intended for commercial entities, that is, companies that trade or sell goods or services."
While the word "companies" appeared in the descriptive text, the root concept was commercial activity. An enterprise did not need a specific corporate charter, such as an LLC, PLC, or Inc., to belong in the category. The design was purely taxometric. If an organization transacted business or sold products, it was commercial. If it governed, it was governmental. If it educated students, it was educational.
Other persistent myths claim the suffix stood for "communication" or "computer." Neither word ever appeared in early DNS architectural papers as a proposed domain class. Those ideas were retrofitted decades later by casual users attempting to explain why the entire internet seemed to route through three letters.
