incredibly

A degree word that sits in front of an adjective or another adverb and pushes it up the scale: incredibly wealthy, incredibly difficult, incredibly quickly. The disbelief has faded. Nobody doubts the wealth; it is simply very great. It suits words that come in degrees: something can be incredibly tall, but hardly incredibly dead. In most places it can trade with extremely without changing the meaning.

Here the word comments on the whole statement rather than on a single word. The speaker finds the fact astonishing and vouches for it anyway. It typically opens the sentence, followed by a comma (Incredibly, no one was hurt), or sits between commas in the middle. Without those commas, a reader may take it as modifying the next word, as the intensifier does. The punctuation does real work.

The literal sense, built straight from incredible plus -ly. It judges the way something is done or said as beyond belief. Bruce Mansfield's Australian Democrat (1965) has O'Sullivan speaking "incredibly of eighty-five 'enrolled' members": the boast itself strains belief, not the way he delivers it. This sense usually follows a verb. Before an adjective or another adverb, the word is usually the "extremely" intensifier instead.