I'm looking for a specific word (that is slipping my mind) that means "not allowed to be changed" or "has to be taken as law". The word I'm thinking of sounds something like "invaluable" or "inviable". An example of how to use it would be "Since the CEO likes it, this feature is ___ "

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    Rather than inviable (something which is not viable), I think you were going for inviolable (something which can not be violated). Commented Dec 5, 2019 at 10:01
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    Synonyms of compulsory // 'antonyms' of optional. Commented Dec 5, 2019 at 13:03
  • I like "untouchable" the most in your example. It depends if you want a negative connotation; could also try "unmodifiable" or "stagnant". Since you shared your like-sounding words, inviolable is probably the correct answer.
    – minseong
    Commented Dec 5, 2019 at 20:51
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    Hmm I'd go with "sacrosanct" myself.... Commented Dec 6, 2019 at 2:41
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    There is a Latin expression often used in law: "sine qua non", meaning literally 'without which there won't be', or more comprehensively 'it won't happen without it'. Another legal term also is entrenched clause.
    – user369016
    Commented Dec 6, 2019 at 10:52

17 Answers 17


You can use the adjective immutable:

unchanging over time or unable to be changed.

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    This means "cannot be changed", which is stronger then the requested "should not be changed".
    – MSalters
    Commented Dec 5, 2019 at 12:11
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    Yea, "immutable" does not quite capture the human power dynamics of OP's request. Commented Dec 5, 2019 at 16:19
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    @MSalters IMO the OP's own answer indicates that the intended meaning was much closer to "cannot" than to "should not". People often say "cannot" when the reality is that they can but would not like the consequences. This seems to me to be one of those cases. I think the main defect in this answer is that the proposed word does not sound like "inviolable."
    – David K
    Commented Dec 6, 2019 at 1:45
  • I guess I interpreted the question more strongly than some people, but I think the intent of the question was to get a word that's more stronger than just "should". They key words in the question for this are "must", "law", and "CEO". Particularly that last word :P
    – Laurel
    Commented Dec 6, 2019 at 3:14
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    const or readonly are candidates too in the right context :-)
    – Zimano
    Commented Dec 6, 2019 at 20:02

Got it- the word is "inviolable"

Definition from Merriam Webster:

1: secure from violation or profanation
2: secure from assault or trespass

"Inviolable" at first glance doesn't precisely fit my example sentence: "Since the CEO likes it, this feature is ___ ". However, when emphasizing the importance of the feature in question- to the point of making it sacrosanct- the word works.

  • I've thought a bit more on the matter and changed my mind. In the example's case, a feature (from a software development view) cannot really be violated (by the developers because the feature doesn't exist yet) and thus doesn't really need security from violation. I think your question actually already has the answer, which is invaluable. If it was company policy for example (since it actually is a ruleset or guidance), inviolable would be much more appropriate imho. Commented Dec 6, 2019 at 14:50

Stretching the definition of "single word" slightly, and it doesn't sound like the word you were thinking of, but perhaps (depending on the context) non-negotiable might do?

Since the CEO likes it, this feature is non-negotiable.

Which would work well if the context is something like:

We need to remove some features from this release due to time constraints. Can <this feature> be removed?

Sorry, since the CEO likes it, this feature is non-negotiable.

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    This is a better choice than all the answers imho, should've thought of that sooner. (Yes, that includes mine.) Commented Dec 5, 2019 at 11:27
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    @JohnHamilton - If it helps, I'd say this and yours are tied for the best here. :-) Commented Dec 5, 2019 at 12:55
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    I'd say a word with a hyphen counts as a single word
    – jcollum
    Commented Dec 7, 2019 at 0:28

This isn't a single-word answer because it sounds more natural, especially in speech, to say that a thing is "set in stone" rather than using a single-word. It's also short enough that it doesn't disrupt the flow of the sentence. Also, Merriam-Webster has a few alternatives for this phrase.

So, my answer would be:

Since the CEO likes it, this feature is set in stone.

Cambridge definition (emphasis mine):

set in stone

to be very difficult or impossible to change:

The schedule isn’t set in stone, but we’d like to stick to it pretty closely

A very similar alternative, albeit strange sounding in spoken English, is enshrined. (Thanks to Peter for the suggestion.)

From Merriam-Webster (emphasis mine):

Examples of enshrine in a Sentence:

  • Some teachers tend to enshrine their personal preferences as sacred rules of English grammar.

  • By the time the monarchy was restored in 1660, the idea had taken hold that the spaces should be open to the public, a concept that was eventually enshrined in law in 1851.

Another alternative is must-have

Since the CEO likes it, this feature is a must-have.

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    Very similar: Enshrined. Commented Dec 5, 2019 at 8:44
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    I took the liberty of formatting the quotation. :-) Commented Dec 5, 2019 at 10:33
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    I like this answer. Idioms are an important part of the language. They have to be used more. Commented Dec 5, 2019 at 14:22
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    Since the original question specifies a single word request, this answer is technically not correct, so someone will probably downvote for that reason.
    – barbecue
    Commented Dec 5, 2019 at 21:54
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    Along the same lines as "a must-have", my first thought was "a must"
    – wjandrea
    Commented Dec 6, 2019 at 18:37

It doesn't sound like the other words in form, but you might be looking for something like "mandatory".

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    "Mandated", perhaps? Commented Dec 6, 2019 at 14:07


From Cambridge:


so important that there cannot be any change or question

Based on your description, I think this fits your criteria.

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    I agree... saw your answer after I commented... Commented Dec 6, 2019 at 2:42

'fixed' or 'static' would be my choice

As immutable is already mentioned.

  • It would improve your answer to include an explanation of why you consider this a good choice and also include a reference/dictionary link. Commented Dec 5, 2019 at 9:14
  • It's also Laurel's choice - about 11 hours ago
    – mcalex
    Commented Dec 5, 2019 at 9:14
  • Adjusted my answer to include reasoning, links to definitions & to give another answer than already mentioned. Commented Dec 5, 2019 at 10:07
  • In software development, "fixed" has different, more wide-spread, uses and saying a "feature is fixed" could generate a different meaning. I'd advise against its use in the example's context only. Commented Dec 5, 2019 at 11:27
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    Yeah that makes sense, I guess maybe 'required' is probably the term for the example given Commented Dec 5, 2019 at 12:46

I think something along the lines of mandatory, compulsory, or requisite would work best. Use any of these if there are some regulations or guidelines affecting the issue. But I don't think that's what you're going for.

If you're set on keeping the in-/im- prefix try integral (for the feeling of a much needed component) or imperative (for a feeling of urgency/necessity that has come from a command). There's also inflexible and immoveable, but those can be kind of clunky sounding.

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    +1 I believe OP is thinking of the word "Imperative". Commented Dec 5, 2019 at 22:14

Unalterable sounds closer to what you mean, at least to me. Immutable while considered a synonym to unalterable has a more permanent ring to it, meaning even if change was required, it is impossible to happen.

According to the example in this link , there seems to be a condition for change when unalterable is being used as a word.

the constitution was unalterable without the king's consent

So your "not allowed to be changed" aspect of the question means it could be changed if needed, and unalterable seems like the best option.


Axiomatic? Refers to assumptions that are taken as true. "At one time it was axiomatic that you couldn't take the square root of a negative number."

  • I don't think this is what the OP is looking for (doesn't fit the other criteria well), although it was my first thought also for "has to be taken as law".
    – Matthew
    Commented Dec 5, 2019 at 16:08

Working with this constraint:

The word I'm thinking of sounds something like "invaluable" or "inviable"

I think the word you're looking for may be invariant or invariable, although both words don't feel entirely natural to me in your example sentence.


Another option: Obligatory - A single word which describing something that must be included/cannot be left out, either because some authority insists on it, or because of a social convention, more, etc. Something can be obligatory because it is required by law or rule, but it can also be obligatory because it is expected to such a degree that it would be socially or politically unacceptable not to include it.

I didn't go to Ned's pool party because I didn't have the obligatory beer hat.

Compulsory is similar, but with more connotations of an official or legal requirement.


You didn't mention the register the word you're looking for must belong to. If you're being informal, for keeps might work. The Collins English Dictionary defines as follows:

Something that is for keeps is permanent and will not change.

A bunch of examples from Longman Dictionary:

Marriage ought to be for keeps.

He's given it to me for keeps.

The specific word that you have in mind but have forgotten might be irreversible:

Not able to be undone or altered.


She suffered irreversible damage to her health.


The only specific single word I can think of is: "Decided" - As in: "The matter has been decided." (passive voice, not mentioning who/what decided)

Using more than one word is probably going to work out better for you though.


It all depends on context, of course, but "unchangeable" ("not able to be altered," which could also be "unalterable") is understandable and precise.

I think "sacrosanct" is a great answer for the context given in the question. But it does have a religious or moral connotation. Then again, we're talking about a human hierarchy and authority (a CEO's preference), so it's not a purely technical scenario. Contrast that with the orbit of a planet governed by laws of physics, which I would not say are "sacrosanct" but could be called "unchangeable" or "inviolable."


Possibilities include constant and eternal.


you can use any of this:

  1. constant

  2. fait accompli

  3. forbidden

  4. firm : steady and not likely to change

And the top most is "final"

Since the CEO likes it, this feature is final! It's because if something is final, it cannot be changed.

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