Ouroboros divides the time into epochs, and each epoch is divided into slots. A slot is a short period of time of about 20 seconds.
Credit: Cardano papers ( https://cardanodocs.com/cardano/proof-of-stake/ )
A slot has only one Slot Leader (SL).
The slot leader has a (sole) right to produce one and only one block during their slot.
The number of slot leaders is equal to the number of slots in the epoch and if a slot leader missed their slot, they will lose the right to produce a block. To produce a block, they need to be elected again.
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