demum

Demum is an adverb that adds no meaning of its own; it sharpens the word immediately in front of it. After a time word it narrows the moment to that one and no earlier: tum demum, "only then, not before"; nunc demum, "now at last". After a pronoun or an adjective it narrows the reference the same way: is demum vir, "he and only he is the man".

That is why it is a mistake to file it as a synonym of tandem. Tandem is impatient, the sigh of a speaker who has waited too long; demum is merely exact, and a sentence with demum in it is usually excluding alternatives rather than complaining. It is indeclinable, sits after its word, and never begins a clause on its own.