Although non-valid and invalid have the same meaning semantically, I tend to interpret them with a subtle difference.
The difference is the same as that between words like "not useful" and "useless". Calling something "useless" seems to me like a more blatant/harsh way of negating its usefulness than calling something "not useful".
Similarly, I tend to interpret "non-valid" as simply negating the validity of the subject (less intense) and "invalid" as harshly specifying that something is invalid (more intense).
While there would be no book or rule stating this kind of a difference, I believe that our brain inadvertently picks up this kind of cognizance by reading text and observing the minute difference in ways these words are used.
It would be interesting to know if others also feel the same way.
Answer from satnam on Stack ExchangeAlthough non-valid and invalid have the same meaning semantically, I tend to interpret them with a subtle difference.
The difference is the same as that between words like "not useful" and "useless". Calling something "useless" seems to me like a more blatant/harsh way of negating its usefulness than calling something "not useful".
Similarly, I tend to interpret "non-valid" as simply negating the validity of the subject (less intense) and "invalid" as harshly specifying that something is invalid (more intense).
While there would be no book or rule stating this kind of a difference, I believe that our brain inadvertently picks up this kind of cognizance by reading text and observing the minute difference in ways these words are used.
It would be interesting to know if others also feel the same way.
This is an intriguing question. My experience is much like satnam's, only sort of the opposite. The two terms have such similar meanings that dictionaries often use one term to describe the other. There does seem to be a subtle difference in actual usage that I can't find formally documented, and it somewhat relates to a matter of degree. Where our experience differs is that I think of non-valid as the more "intense" term, to use the same adjective. Perhaps it's very situation-specific. Here's my crude attempt to characterize it.
"Invalid" seems to be used to refer to something that is not currently valid or that a reasonable person might mistake for valid, whereas "non-valid" seems to be used to refer to something that under no circumstances could ever be valid. Some examples:
- An invalid license could be an expired license. It was previously valid and could be made valid again via renewal. A non-valid license could be a foreign license that can never be valid.
- An invalid credit card might refer to one that used to be valid but has been cancelled or expired. A non-valid credit card might refer to a credit card that is not one of the brands the merchant accepts.
When a term for validity is applied to an assumption or argument, "invalid" seems to be reserved for incorrect ones a reasonable person might mistakenly make, while "non-valid", if it was used in that context, would cover cases more not valid.
For example, in a serious discussion or debate, one person uses an assumption or argument that seems reasonable on the surface but can be demonstrated to be incorrect. That would typically be referred to as "invalid". Use of "non-valid" would more likely be applied to a more obviously bad assumption or argument where the person making it is expected to know better.
Another example: "Why is John taller than Bob?" "Because Tuesday." People wouldn't be likely to talk about the "validity" of such a response because the argument is so far away from being valid that validity is irrelevant. But I suspect that if someone was to apply "invalid" or "non-valid" to it, the terms would elicit different reactions. "Invalid" would seem so misapplied that people would assume it was sarcasm, even though it is technically true. "Non-valid" would just sound odd, perhaps leading people to wonder if it was some kind of clinical observation rather than off-the-cuff commentary about the content.
So I am also curious to see other responses to the question.
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invalid there is a noun.
invalid (n) - Someone who is incapacitated by a chronic illness or injury.
Having this said, his wife seems to be very sick, in a crucial condition that might have made her incapacitated.
Now since there's discussion about the degree of being incapacitated (which makes you ultimately invalid), I'm adding a bit to improve this answer.
Here is another reference from OLD:
invalid (n) - a person who needs other people to take care of them, because of illness that they have had for a long time.
Now, if you look at both the definitions, you see that the term invalid ranges from someone being assisted by others to walk, eat or do routine activity to someone who is permanently bedridden (as in the last stage of cancers). Contrary to what Doc and FumbleFingers, it is not always necessary that invalid person is so so so sick that he/she is on the deathbed. And, I'm a doctor and have come across many such patients with chronic illness (in fact, have worked in hospitals that only take such cases).
The OLD further explains it in its example:
She had been a delicate child and her parents had treated her as an invalid
Furthermore, delicate here means:
delicate (n) - (of a person) not strong and easily becoming sick
That's where the WordWeb definition fits in. Invalid is someone who is incapacitated - not able to perform their tasks because of illness that has brought weakness. Here, the child does not necessary to have Ryley's tube or Folly's catheter as Doc mentions.
On the other hand, invalid does not always mean that the person is just incapable to do things and is not so critical. That's why I said, the term applies to incapacitation and this varies from degree to degree depending on the illness that person has.
Check this here:
If you see Saturnino Soncko (a person working in the silver mines of Cerro Rico), he's certainly invalid but I can still argue and deny calling him invalid as at least he is not that incapacitated! In that picture at least he is sitting without any assistance whereas invalid requires support even for this, don't they? They certainly do I see the woman every day. She is an invalid and cannot move anything other than her eyes.
Again, invalid is certainly a serious condition but it varies in degrees or severity depending upon the type of illness. I'm not sure to apply partially invalid or completely invalid for that though it might make better sense.
An invalid, pronounced with stress on the first syllable, is a person with a disability. The word is not used so often nowadays.
It is a noun and a different word to the adjective invalid, pronounced with stress on the second syllable, which means not valid.
So the last sentence of your question "Your husband is invalid" is incorrect, it would be "Your husband is an invalid".