This is from a For Dummies series book. I don't think I understand the phrasing of this title. When is a virtual function not... not what? I presume this must be some kind of a pun.

A friend of mine, who is a native speaker from America, could only say that this reminded him of the joke "when is a door not a door", but he was not at all sure whether that was what the author was going for.

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    Linguistically, this process of omitting syntactic constituents is known as deletion (jargon for the linguistic process of ellipsis, not for hitting the Delete key on the keyboard). The text there is about situations in which what is believed to be a virtual function (because it has been declared one) is actually not a virtual function in the way it behaves. So, when is a virtual function not {syntactic deletion: a virtual function}.
    – TimR
    Commented Jul 25, 2016 at 12:29
  • To be perfectly honest, I don't care much about what it's called. What I care about the most is the mechanics of how things work. Whether you call it deletion or ellipses is not going to make a big difference to me. Why do you need to omit anything in the first place? The sentence sounds incomplete. Period. Commented Jul 25, 2016 at 13:09
  • @CookieMonster "When is a virtual function not {virtual}?" (Note: the deletion is only of "virtual." I think both TRomano and Javalatte have it slightly wrong here.) The play on words depends on the reader thinking of virtual function as a discrete entity. For instance, I might entitle a piece about a bad camping experience: "When is a Happy Camper Not?" Commented Jul 25, 2016 at 23:39
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    A rule of thumb I often employ is, "When you see some strangely worded phrase presented in an uncommon, frilled font, don't spend too much time wrestling with the grammar." You may as well ask why the author didn't choose Times New Roman for their headings. The author gets to do what the author wants, whether you understand or not is secondary. It means when is a virtual function not a virtual function as explained by many here and by the author in the first two sentences following the header.
    – EllieK
    Commented Aug 3, 2016 at 19:44
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    It does sound incomplete to me as well. The basic purpose of ellipsis is to avoid repeating words. In this case I think it bleeds more into the jokey realm away from "proper" English. I suggest you go read the wikipedia entry for all kinds of categories of ellipsis and you'll also find interesting examples where the language doesn't allow it. Not all of the theory is well understood.
    – shawnt00
    Commented Aug 12, 2016 at 14:09

2 Answers 2


This play on words depends both upon the reader's acquaintance with the meaning of the phrase Virtual Function, and here upon the currency of that phrase in the jargon of a specialized audience. In English, as in most languages, humor (however mild it may be, as in this example) sometimes depends for its success upon eliciting surprise in, or confounding the expectation of, the reader: here an expected modifer in a well known phrase is omitted from the title sentence, and this comes as a (mild) surprise. If there were a term for this particular form of deletion, it might be predictive ellipsis,† or, taking a page from medical usage, phantom ellipsis.

The article here describes functions which appear to be Virtual Functions, but which, upon analysis, are not. The modifier in the common phrase, Virtual, is deleted from the sentence as written, but the reader, expecting it to follow the negation, perceives the question as When is a Virtual Function Not (Virtual)?

The same device might be employed in precisely the same way in the title of an article about a substandard campground:

When is a Happy Camper Not?

Another example might be the title of an article which describes a particularly boring National Football League championship contest in the U.S:

Why Was The Super Bowl Not?

Note that this device will not be effective when the phrase employed has no "identity" of its own as a well known phrase, as in:

When is a Green Taxi Not?

† In the event that this form of deletion has no name, I will accept credit for either coinage. If, as I suspect, there is a term already in use, I do not doubt that it will be provided in commentary.

  • This is a possible interpretation among other possible interpretations. Commented Aug 8, 2016 at 6:25
  • @CookieMonster Are you going to award the bounty? Commented Aug 10, 2016 at 5:00
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    Not yet. No offense, but your answers is still a poor explanation. It explains nothing, really. You're beating around the bush with phraseology and not explaining the actual mechanics. Give me examples from real speech. An example of a conversation where a person can actually employ that kind of phrasing. Commented Aug 10, 2016 at 7:23
  • I provided an explanation of the way this particular device works in English. Since this device, I believe, has never really been described before, I invented my own "phraseology." It's important for you to understand that this usage would never be encountered in natural speech. The mechanics are described clearly, it seems to me: WH-word+is/was +Common phrase+not+(modifier from phrase.) It's actually rather simple, and it's the kind of device that would only be used in writing a headline, such as in the example you provided. I'm pretty sure this is the best you're going to get. Good luck! Commented Aug 10, 2016 at 8:42
  • It is a matter of interpretation whether what is left out of the sentence is virtual, as this answer says, or a virtual function as @JavaLatte has said. I don't see the former version as being part of a "well known" formulation. The only examples are not backed by any sources. In fact, I think when taking about ellipsis, one provides as much material as possible to complete the sentence. For example, what is missing from Joe is just as tall as Tom? One could say is, but is tall is a more complete version. Joe is just as tall as Tom is tall. Commented Aug 10, 2016 at 12:37

If written out in full, the title might be

When is a virtual function not [a virtual function].

If a part of a sentence is repeated later in the sentence, it can be omitted, as long as the meaning is still clear. This is called ellipsis or deletion.

Ellipsis can only be effective if the listener or reader can easily tell what has been omitted. For example:

He says that instant coffee tastes the same as expresso, but it doesn't.

We parse the sentence and realise something is missing: we understand what the speaker or writer wants to say, and can easily fill in taste the same.

In the example you provided, we realise that something is missing, but we don't understand what the writer is trying to say. We can guess, but even when we do that we don't understand, because we have not read the chapter that explains this. Even having read the chapter, there are at least two possibilities for what the omitted text should be: a virtual function, or virtual.

The writer is trying to grab our attention by using a headline that adds a bit of mystery to an otherwise dull subject: the technical term for this is a Teaser Headline.

The wording suggests that the title may also be intended as an oblique reference to a certain type of children's joke, and the use of ellipsis is supposed to add to the humorous effect. Here is a typical example of this type of joke:

When is a door not a door?
When it's ajar

The joke is not a good one, and the use of ellipsis is in this case confusing. Arguably, the headline is an effective teaser, but because of the levels of confusion that go into its construction, it may be more irritating than intriguing.

  • Who did you learn that rule from? I know what ellipsis is. I think you're taking it too far. Commented Jul 25, 2016 at 11:53
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    @CookieMonster: don't shoot the messenger. I didn't write that crappy title: I'm just trying to explain what it means. I have added something to my answer to explain what was probably going through the writer's mind.
    – JavaLatte
    Commented Jul 25, 2016 at 11:58
  • Which rule are you talking about? I don't see any rules presented by JavaLatte. If you click on the highlighted word "ellipsis" you can read the entire Wiki article. I don't think anyone is taking anything too far. I think someone is being caustic and resistant and playing devil's advocate.
    – EllieK
    Commented Aug 3, 2016 at 20:00
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    JavaLatte - The "door not a door" joke has nothing at all in common with the device presented by @CookieMonster . Only one word is omitted: the modifier Virtual. The phrase a virtual function is not omitted. That is critical to this particular kind of play on words. It would not work with, for instance, When is a Green Taxi Not? - because the device depends upon the modifier's rôle as an integral part of the "well-known" phrase. Commented Aug 8, 2016 at 5:05
  • @P.E.Dant. I agree that it is not structurally identical, but I never said that it was.
    – JavaLatte
    Commented Aug 8, 2016 at 10:48

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