Microsoft Word insists that it should be but I don't know why.

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    To the closers: "Commonly-available references" mention that this is a trademark, but none that I checked explicitly answer the question of why it needs to be capitalized. To some of us the connection is obvious, but just as obviously, it is not clear to everyone. Hence some people ask the question, and the references do not obviously answer it. The reason for excluding questions that are answered by commonly-available references to exclude things like "what does Ethernet mean?" not to exclude questions like this.
    – iconoclast
    Commented Aug 19, 2016 at 3:53
  • 3
    Unless you can demonstrate that it is obviously and clearly answered by commonly-available references, there are no grounds for closing it.
    – iconoclast
    Commented Aug 19, 2016 at 3:54
  • 2
    This is a question of enduring interest to people who read and write about computers and computing—and usage is not nearly as settled as the lone answer below might lead one to believe.
    – Sven Yargs
    Commented Feb 7, 2021 at 20:15
  • 1
    cpit's amazing and thorough answer illustrates how, while compulsive closers look superficially at questions and dismiss them quickly, people who look deeply into them show there's a lot of important information worth exploring. Thank you @cpit!
    – iconoclast
    Commented Mar 23, 2022 at 18:50
  • Never capitalize it myself. Not going to follow the herd. Even if most people capitalize it now history will be on my side. Try googling on the internet for the verb “to photoshop”.
    – David
    Commented Mar 23, 2022 at 19:43

2 Answers 2


Short answer:
The word ethernet is capitalized because Ethernet is the currently accepted convention.

Longer—but still not entirely satisfying—answer:
The reason Ethernet is the current convention remains unclear. Authoritative explanations are absent or inconsistent. It cannot be explained by trademark status or by comparison to similar examples. Nevertheless, the convention itself is surprisingly consistent.

Trademark status

Ethernet does not appear to be an active registered trademark. (Disclaimer: I'm not well-versed in trademark application procedure or terms, but the following is what I could gather.) Application for ownership of the mark ETHERNET was filed on behalf of Xerox Corporation in 1979 and registered in 1981. The trademark applies to goods classified as "apparatus and instruments," described in the application as "Electronic Communications Networks, Transmitters, Receivers, Cables and Controllers." The trademark was cancelled in 1988 after Xerox did not file a declaration under Section 8 of U.S. trademark law, which requires an affirmation stating the mark "is in use in commerce." Subsequent to Xerox's lapse in ownership, two applications to trademark ETHERNET have been filed. Unlike Xerox's trademark, which applied to goods, the newer filings applied to services. The applications were made on behalf of different LLCs with the same physical address, the first in 2011 for "Provision of access to the internet" and the second in 2013 for "Telecommunications services, namely, Internet access provider services."* Neither trademark is in force: both applications have a status of "Dismissed or Invalidated" because of failed or late responses to the Trademark Office.


In any case, the existence of a trademark for Ethernet would not necessarily explain its capitalization. Trademarks can become genericized, even in the face of corporate strategies to counteract genericization. Wikipedia's list of generic and genericized trademarks, for example, lists Xerox® and Kleenex® under "protected trademarks frequently used as generic terms." A quick internet search of style guides suggests Xerox and Kleenex are commonly used as examples of trademarks that should be capitalized. The section on trademarks (§8.153) in The Chicago Manual of Style lists both as examples of trademarks that should be capitalized (if their use cannot be avoided), but also notes that Webster's differentiates the verbs xerox and google, among others, which are not capitalized. However, in Microsoft® Word with AutoCorrect enabled, typing use kleenex on the xerox copier is corrected to Use Kleenex on the xerox copier. Word does not appear to capitalize any use of xerox, independent of part of speech, including xerox corporation. Thus, even for these two widely cited examples, agreement is not universal.

Compare to I/internet

The words internet and web have undergone a change somewhat similar to ethernet, though the conventions are not settled and there isn't consensus on what explains the changes. One style guide for online writing specifies Ethernet, without explanation, while noting that "Per [Associated Press] Stylebook 2016, internet is no longer capitalized." (This same guide capitalizes Google, Googling, and Googled.) The SUSE style guide insists on Ethernet; the guide gives reasons for rejecting some terminological variations (e.g. "Ethernet card" is preferred to "wired card" because the latter "sounds as if wires attached to the card are meant"), but does not specify the reason for preferring Ethernet. Chicago's section "Terms like 'web' and 'internet'" (§7.80) maintains that "Ethernet (a trademark)" should be capitalized. Unlike the cases of Xerox and Kleenex, agreement on Ethernet seems near universal, though explanation is inconsistent. And while Chicago explains Ethernet with reference to its trademark status, it could just as plausibly now be written ethernet given that it has been effectively genericized and, if my research above is correct, it's no longer a registered trademark.

Because convention

Does Ethernet "need to be" capitalized? Apparently not. Xerox did not renew its trademark on ETHERNET though presumably it could have, since the instruments in the trademark application were in commercial use at the time of its cancellation. Had Xerox renewed the ethernet trademark, it could have campaigned against genericization, as it has done with Xerox. The case of ethernet appears to be an unusual one in which the mark's capitalized form, denoting intellectual property, has been retained despite its de facto genericization and de jure loss of proprietary status.

Is Ethernet capitalized? Apparently so. Style guides tend to prefer it. Thus, according to Google Ngrams, Ethernet is by far the most frequently indexed variation, although others less common than ethernet (e.g., EtherNet, EtherNET) have also been indexed. Thus, style guides tend to prefer it, and so on. In other words, ethernet is capitalized because most writing capitalizes Ethernet. Why does Word correct ethernet? Because it's (usually) capitalized.

* Note the differing capitalizations of "internet" between applications, with the later one capitalized.
  • 1
    Thanks. Changed the first sentence under Genericization to hopefully be more accurate. Interesting though that e.g. Xerox and Google, still active trademarks, have undergone genericization to some extent in that their verb forms are not typically capitalized (they aren't corrected by Word), though the UCLA online writing style guide specifies "Googled".
    – cpit
    Commented Feb 12, 2021 at 19:47
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    "Because convention" is really the perfect answer for so many things. The genesis of the convention may or may not be logical, and the circumstances that made it logical may no longer exist ("Ethernet" being a perfect example), but this is the real answer in this case and in so many others.
    – iconoclast
    Commented Mar 23, 2022 at 18:36
  • "iconoclast ie 'Acceptability is usage- and thus user-driven'. Commented Mar 23, 2022 at 19:49

I've seen it both ways. Since it's a trademark, however, it should technically be capitalized.

  • You might want to include this chart to "prove" that the vast majority of published writing contexts do in fact reflect the "technically correct" capitalization. Commented Mar 22, 2016 at 19:23
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    ...but I wouldn't like to say that's necessarily "because it's a trademark". The capitalized version of hoover the carpet is so rare it can't even be graphed on Google Books. Commented Mar 22, 2016 at 19:27
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    In general when something is verbified, it seems to lose the capitalization. E.g. "Did you google him?" "This picture looks photoshopped." "I made a xerox of that article." Not to say that capitalizing would make the statements wrong. But I'm no expert.
    – Hefewe1zen
    Commented Mar 22, 2016 at 19:44
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    It is not accurate to say that you must capitalize it because it is a trademark. Nor is it accurate to say you must capitalize it because it is a proper noun. There are proper nouns that are properly written with a lower case initial letter (some names with van, von, vander, della, del, and so forth), and there are trademarks that are properly written with a lower case initial letter (iPhone, iMac, iPod, iPad). It would be more accurate to say "Trademarks should be written in the way they are trademarked, and proper nouns should be written in the way the owner writes them."
    – iconoclast
    Commented Aug 19, 2016 at 4:07
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    It's not accurate to say it is a trademark. It was at one point, but is no longer legally protected. In any case, as @iconoclast points out, trademark status doesn't necessitate/justify capitalization (cf. Xerox), so to say it should "technically" be capitalized is also inaccurate (and ambiguous--according to which technic?).
    – cpit
    Commented Mar 23, 2022 at 6:06

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