irreparable
Impossible to fix or bring back to how it was.
Irreparable means damaged beyond fixing or impossible to repair. When something is irreparable, no amount of glue, tape, tools, or effort can restore it to what it was before.
If you accidentally shatter your grandmother's antique vase into dozens of tiny pieces, the damage might be irreparable. You could try to glue it back together, but it would never be the same. When a flood destroys family photo albums, that loss is irreparable because those specific moments can never be recreated.
The word often describes serious damage, not minor problems. A torn page in a book is repairable with tape. But if that book falls into a bonfire and burns to ash, the damage is irreparable.
The word also applies to relationships and trust. If someone betrays a friend's confidence repeatedly, they might do irreparable harm to that friendship. The trust, once completely broken, cannot be rebuilt no matter how many apologies follow.