;
Within indexing brackets, ; separates axes. Empty fields select whole axes.
m←2 3⍴⍳6 ⋄ m[2;1] ⍝ 4 m←2 3⍴⍳6 ⋄ m[;2] ⍝ 2 5 m←2 3⍴⍳6 ⋄ m[1;] ⍝ 1 2 3