How is "배우자다" conjugated?
It's 배우자 + 이다 in written/plain form, remain as in its dictionary form when gets added to a consonant, but when it gets added to a vowel 이 can be omitted.
배우자 + 이다 = 배우자이다 or 배우자다 - both acceptable.
빵 + 이다 = 빵이다.
how come we don't have to conjugate the form dictionary form here and can add 다 straight away? is 이다 an exception ?
You don't have to add 다, or anything else, because adjectives in the Written form in Present tense remain the same as in a dictionary.
이다 and 있다 are also adjectives.
아내 또는 남편이 배우자입니다 why is this wrong? duo....
Confused about the usage of 또 here?
또는 here means "or".
It's different from 또 (again, once more).
또 is an adverb that means again.
또한 is an adverb that links two phrase or sentences. Sometimes it can be 'Plus, ...'
I think the right adverb to mean "OR" is " 나/이나" or also " 하거나".