The term 'collect into a mass' can be expressed in four different ways, each with a different number of letters. The first is 'AGGREGATE' with 9 letters, which means to gather together into a single group or mass. The second is 'AMASS' with 5 letters, which means to accumulate or gather together a large quantity of something. The third is 'CONGREGATE' with 10 letters, which means to come together in a group or crowd. The fourth is 'AGGLOMERATE' with 11 letters, which means to gather together into a cluster or heap.