"This is my wife."
Translation:To jest moja żona.
While technically it makes sense one could argue that it is more colloquial with the lack of the verb być
It's not colloquial, it has the same meaning. In a very formal reunion you can say To moja żona. The jest part in certain situations make you feel that the one that says it is a foreigner.
In the sentence "this is" this has different function, than in the sentence "that woman is". That is is always "TO jest" while "that woman is" = "Ta/tamta kobieta jest", "That man is" = Ten/tamten mężczyzna jest
The explanation is wrong. 'that woman' in polish would be 'tamta kobieta', while 'this woman' would be 'ta kobieta'. To refer to objects including people, masculine and femenine genders are not considered, to moja lampa, to moj przyjaciel, to moje okno, etc. TO kind of means this thing in here that is my... The same when someone wants to say in english 'It's me' you use IT to refer to I.
Your explanation is good, but "that" can be translated to both "ten/ta/to" and "tamten/tamta/tamto" depending on context. (I edited my post to include this.
ten, ten, tamten in Polish
this, that, that in English
No. In a "This is Y" sentence, where "this" is a dummy pronoun serving as the subject of the sentence, Y is in Nominative.
If it was an "X is Y" sentence, like "Julia is my wife", Y would be in Instrumental: Julia jest moją żoną.
More info here: https://www.duolingo.com/comment/16373167
Thanks. I already did a bit of digging and found that very post – extremely helpful! And I realized that of course it's actually the same in English, cf. "This is he."