Narrow openings or grooves where something can fit or slide in; also machines where you put money in hoping to win, or designated time periods for activities.
From Middle Dutch 'slot' or German 'Schloss' meaning a bolt or fastening. The word evolved from the physical opening to the machine to the concept of time allocation.
Slot machines were designed by psychology experts to be addictive—the random rewards trigger the same brain chemicals as drugs, which is why they're called 'the crack cocaine of gambling'!
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