The term 'length of time' can be described in four different ways. The first is 'SPAN, ' which is a four-letter word meaning the amount of time between two points or events. The second is 'DURATION, ' an eight-letter word referring to the amount of time something lasts. The third is 'SPELL, ' a five-letter word meaning a PERIOD of time during which something happens. Finally, the fourth is 'PERIOD, ' a six-letter word meaning a length of time marked by specific characteristics or events.