Questions & Answers about Moja sestra i ja sada idemo zajedno u grad.
Because moja has to agree with sestra.
In Serbian, possessive words like moj / moja / moje change according to the gender, number, and case of the noun they describe.
- sestra is feminine singular
- so the correct form is moja
Compare:
- moj brat = my brother
- moja sestra = my sister
- moje dete = my child
So moja sestra is simply the feminine form needed here.
Because the speaker wants to say exactly my sister and I, not just we.
- mi = we
- moja sestra i ja = my sister and I
Both are possible, but they are not equally specific:
- Mi sada idemo zajedno u grad. = We are going to town now/together.
- Moja sestra i ja sada idemo zajedno u grad. = My sister and I are going to town together now.
Serbian often leaves pronouns out when the verb already shows the subject, but here the full phrase is used to name the people clearly.