The term 'SIGMA's Follower' can be solved by the three-letter word 'TAU'. SIGMA and TAU are two of the most commonly used letters in the Greek alphabet. They are often used to represent mathematical constants or concepts, such as the sum of a series or the ratio of a circle's circumference to its diameter. In addition, they are also used to represent the 24th and 25th letters of the Greek alphabet, respectively.