What is the difference between 10-wire 4-wire encoder and 8-wire 3-wire encoder？

3-8 encoder. Input 3 lines, the signal states are respectively 000, 001, 010,...110, 111, a total of 8 kinds, in the output of the 8 lines, corresponding to the level of 1 line is the effective level. 10-wire 4-wire encoder is to encode nine data lines into four-wire (8-4-2-1) BCD.