Quote Originally Posted by Marcus View Post
Why? Or mother tongue = mother's tongue?
In this case, both. Except that she has three mother tongues - besides Finnish, English (father's tongue), and Swedish (local, social and national environment, ie all day every day, from birth).

We used to have fun on the tube. Mum, speaking Finnish to her two daughters and them speaking Finnish to her. Mum and my stepdaughter speaking to me in Swedish (against my wishes, but что делать?), and me and my daughter speaking English to each other. All of us understanding everything that was said, and switching in mid-flow, sometimes in mid-sentence. Little things