Ambiguous loss is loss without closure: a missing person, an estranged parent who's still alive, a partner with dementia who is present but unreachable, an adoption, an addiction.
It's uniquely hard because there's no funeral, no ritual, and often no social recognition. People don't send cards for it.
The goal isn't closure — closure may never be available. The goal is learning to hold both: they're gone and they're here, it's over and it isn't.
Making your own ritual helps: a date you mark, a letter you write, a candle you light. Recognition you give yourself still counts.