The "cadence" is a musical formula (which can be melodic, but is much more frequently, harmonic) which occurs at the end of a composition, a movement, or a melodic entity. Just as prose is formed in phrases, sentences, paragraphs, chapters, etc., music is grouped by certain melodic, rhytmic, or harmonic formulas for each type of rest or resolution.
At the conclusion of the recapitulation in the first movement of Beethoven's Fifth Symphony, we wait for the final cadence which is to close the movement. Instead, Beethoven omits the cadence, so as to be able to continue the movement. He just hasn't completed it yet...
