admodum

Admodum is ad plus modum, "up to the measure", and it behaves exactly as that suggests: it takes a word to its full extent. With an adjective or adverb it intensifies, admodum parvus, "very small indeed". With a numeral it means "fully, quite as many as", so admodum mille is a thousand and not a rough estimate.

With a negative it strengthens the denial rather than softening it: nihil admodum, "nothing at all". Standing alone as an answer it means "quite so, certainly", which is how it works in dialogue. It never governs a case; the accusative modum buried inside it is already accounted for, and treating admodum as a preposition is a common beginner's error.