Is there an adjective that describes something that must be omitted/absent in a particular context?

For example, consider this software documentation that explains the relationship between two different variables:

  • When contentType = 'application/json', schemaVersion is required (must be present).
  • When contentType = 'x-vendor/manifest', schemaVersion is optional (may be present or absent).
  • When contentType = 'image/jpeg', schemaVersion is _______ (must be absent).

What word can be used to fill in the blank?


6 Answers 6


See the W3school definition of the use attribute in XML which is for exactly this characteristic :


[...] Specifies how the attribute is used.
Can be one of the following values:

optional - the attribute is optional (this is default).
prohibited - the attribute cannot be used.
required - the attribute is required.

  • 7
    Ironically, w3school is widely considered to be pretty bad at teaching the languages it is supposed to teach (HTML, CSS, ECMAScript, SQL, PHP, XML, XSLT, …), but hey, at least it teaches English :-D Commented Jan 13, 2017 at 22:53
  • 2
    Ugh, technical people hate that you used w3schools. At least find something at the W3C!
    – ErikE
    Commented Jan 14, 2017 at 0:42
  • 2
    @JörgWMittag: I never understood why it was so hated, I remember reading that people think it has gotten better.
    – user541686
    Commented Jan 14, 2017 at 10:38
  • 2
    @KhalidHussain did that site use to have concrete information about W3Schools? I don't see any now, but I see many people linking to it in conversations about W3Schools.
    – Dan Getz
    Commented Jan 14, 2017 at 19:24
  • 1
    @DanGetz, you may use The Way Back Machine to check out the website at different times, here is an example: web.archive.org/web/20120620135916/http://w3fools.com Commented Jan 17, 2017 at 7:00


forbidden, adj

1 : not permitted or allowed

source: Merriam-Webster online


If you don’t insist on a single word, not allowed works. There’s also disallowed.

Note also some useful in-between words:

  • schemaVersion is recommended (optional, but generally encouraged).
  • schemaVersion is deprecated (optional, but generally discouraged).

I propose the words "excluded" or "disjunct".

I believe you are referring to a case of the exclusive OR -- familiar to the computer science field as an XOR. Philosophical mutual exclusion or mutual disjunction.

I hope that this helps.


They're good answers here already.

I thought to add, "precluded," in case it rings true too.

In the context, the meaning would be that it's prevented from possibility, which I think is the sense that's needed.

See this listing, from Oxford dictionaries online, especially the example sentences there. For instance, "Many reports use research designs with low internal validity, precluding a complete functional analysis."


If we change the wording slightly, we can sidestep the issue entirely by using RFC-2119 terminology 😁

  • When contentType = 'application/json', schemaVersion MUST be present.
  • When contentType = 'x-vendor/manifest', schemaVersion MAY be present.
  • When contentType = 'image/jpeg', schemaVersion MUST NOT be present.

(hat tip to bishop)

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