To state the blindingly obvious a cadenza is the segment in a concerto when all the other instruments stop playing while the soloist(s) gets a chance to show off, developing the themes from the movement and accentuating areas in which their technique is at its best.
My only problem with the definition is how short is too short to be a cadenza.
In our prelim listening there was half a bar where the solo instrument was playing alone and showing off with what sounded like demi-semis. The teacher said that this was to short to be a cadenza yet in the concertos i have heard and all the definitions i have read there has never been a minimum or maximum length for a cadenza.
So i thought i would ask the collective view on how long a cadenza has to be to be a cadenza?
and on another point from the same question how could Basso Continuo be correct when the bass stopped for half a bar?