Robert Lane Greene says that while lists of untranslatable concepts are fun to peruse, in reality, “almost nothing is truly untranslatable”:

Statements of the “no word for” type have two potential implications. One is that “Society X has been without item A for so long that it has no word for it.” Language reflects society, in this view. The other possibility makes language the cause rather than the effect: “Because society X lacks word A, its members are unable to understand A.” Both of these arguments are usually wrong. …

There is no native English word that means ennui, exactly, with its perfect little package of weariness, boredom, emptiness and sadness. So English borrowed it. But does anyone think ennui did not exist among Anglophones before then? Of course not. Does it mean that ennui can’t be explained in English? Again, of course not. (“Weariness, boredom, emptiness and sadness”.) The fact of its borrowing doesn’t make ennui “untranslatable,” nor uniquely French. Language is a little bit like an economy. If a foreign country makes something useful, it’s often easier to import it rather than make it yourself.

(Detail from Almeida Júnior’s 1899 painting Saudade. The Portuguese word roughly translates as “longing.”)