Having lived in France for the last 40 years (next February), I have forgotten quite a bit of unused English and also often missed new words and new slang. Sometimes the words are quite common, but when they are "street language" you don't see them in print or on the internet as much as you would like. One simple example is that I had no idea what a "hoodie" was the first time I saw the term written down.
On my first trip to Europe, I remember a conversation I had in a Swiss train station with an Indian gentleman who's English was so-so after having lived in German for over a decade. He told me that when he went home to visit his mother after 20+ years without using his mother tongue (although there were many Indians around him, that language was spoken by none) in all that time forced him to communicate with here in a more widely used Indian language.
OP, is that what you were wondering?

Thank you for the replies. Yes, viagero, this is what I had in mind. I have a shortwave radio and I used to hear the opening hour of Bhutanese Radio when I lived in Nepal; the trumpet calls and chants of a Buddhist prayer session. Then they would move into news (I assume) in their language. If I was from Bhutan and living in, say Rwanda, I would have no opportunity to use my mother tongue and Radio Bhutan's signal would not stretch to Rwanda..
Kerouac2, yes, very good point, new words are a real 'issue'.
I love the Cambridge Online Dictionary's ever-growing section of 'new words'. It's a constant source of wonder and amusement. And an eye-opener for those who 'don´t like' or 'don´t want' new words 'polluting' the language. What a lost cause that argument is!
I once had a conversation with someone who held this view. I asked them what they called the mobile phone they kept taking out of their pocket. Rather disappointingly, they didn't have an old Norse, Anglo-Saxon or Celtic word ready at hand...
Oddest part of the whole thing? She sent my Aunts to non-maori private schools and refused to allow them to learn Maori.
Not that odd. Similar things happened to Gaelic speakers in Scotland. However, while this is often portrayed as a terrible injustice now, at the time it would have been criminal to deny them learning in English, the passport to the wider world. Otherwise they could have been trapped in a circle of unemployment in a remote place.
My grandmother was prevented from speaking Vosgian when she began school in France. And it was the same for every other regional dialect in France.
Vinny,
forcibly removed
Link, please.
Not everything is learned on the internet. I actually learned about that in school many years ago.

I was born in Russia and moved to the US when I was 5. By the age of 6, I completely forgot the Russian language and mastered English. With the exception of a couple of generic words that I do remember, I'm not sure if I learned then over time or based on memory. If I start to learn Russian again will I be able to pick it up as fast as English because it was my native tongue, or will it take a while? Or is it completely hopeless to learn Russian because the Cyrillic alphabet is so different from English? Well I believe it was the age of 6. I have no memories of Russia or any memories really before the age of 7/8.
Edited by: CrazyAnimal

as fast as English
How long was it before you could speak, read, and write English at your present level? Probably 12-14 years. I thnk if you practice Russian as many hours a day as you practiced English in that time period, you'll learn it faster than you did English. But not because it's your native language.
Of course it's not hopeless because of the different writing systems, English speakers learn Russian, Greek, Hindi, Arabic, Hebrew, Japanese, Chinese etc all the time, and vice versa.