The word "małżeństwo" has two meanings:
małżeństwo - marriage/the institution/the legal act of marriage/the state of the union małżeństwo/para małżeńska/mąż i żona - married couple/husband and wife/spouses
to get married - pobrać się / zawrzeć związek małżeński / związać węzeł małżeński
Jesteśmy pobrani/Jesteśmy związani związkiem małżeńskim - We are married Jesteśmy małżeństwem/Jesteśmy małżonkami - We are a married couple/spouses
When I needed to type this in polish, the correct answer was rejected until I put a full stop at the end, seems a bit harsh!
One week later and it is still happening!
Also, I forgot to add before that this discussion was not linked from the question (I got here by searching) which tried to open the first time I clicked it, but the window self closed and then the button stopped working.
'We are a married couple' is accepted but as 'pair' isn't usually used for a romantic (human) couple, except in the sense of 'a married pair of... jugglers/actors/ice skaters', it isn't accepted. I agree that if plovers could speak and could get married, they might say they are a married pair!
I was sure that a 'noun is adjective only' phrase doesnt decline the adjective's case. Only its gender and its count.
1) Am i correct on that?
2)Since the object here (marriage) is being declined here, its safe to say "marriage" is not an adjective (ie. describing us like "we are tall, we are hungry, we are busy.") It is a noun phrase. (Eg. We are men, we are teachers, we are married)
Is it ok to infer that from the fact that, if its declined for case, then it cant merely be an 'adjective without a noun'?
1) If I understand you correctly, then yes. "Jabłko jest smaczne" just uses an adjective in Nominative.
2) Yes, "małżeństwo" is definitely not an adjective, it's a noun. English may use "We are married", but Polish is closer to "We are a married couple", with 'married couple' being one noun.