Equal Underbar Slash ≢

Monadic Not Equal Underbar means Tally

      ≢ 'a'
1
      ≢ 7 4 2
3
      ≢ 5 4 3⍴0 
5
      ≢ (1 2)(3 4)
2
     mat
1 2 3
4 5 6
      ≢ mat   ⍝ note how "tally"
2
      ⍴ mat   ⍝ differs from "shape"
2 3

Dyadic Not Equal Underbar means Not Match

      'bex' ≢ 'b','e','x' 
0
      1 ≢ 1 1
1