saudade

The Portuguese have a word that other languages keep trying, and failing, to borrow: saudade.

It means longing, but not any longing. It's the longing for something or someone you loved and lost, or perhaps never had. It's the presence of absence. It's nostalgia, but with the knife edge of knowing you can't go back.

Some trace it to the Latin solitatem (solitude). Others to the Arabic sawdā (a black melancholy). But the word became uniquely Portuguese during the Age of Discovery, when sailors left for years—sometimes forever—and those who waited at home had to name what they felt.

Fado music is built on saudade. The Brazilian bossa nova too. No translation captures it because no other culture fermented this particular ache into a single word.