Hiraeth
This word has no equivalent in English - it takes at least a sentence to explain it. And even then, they don't understand.
Ah, Hiraeth. I've had conversations with Mr M about this. Something like, the feeling that only in Wales can you be whole and complete, a Welshman abroad even by his own choosing is always in exile. Or something.
I like the way it is written inside the rugby team's away shirts.