Comma ,
Monadic Comma means
cube ⍝ 3D array
1 2
3 4
5 6
7 8
, cube
1 2 3 4 5 6 7 8
,[2 3] cube ⍝ Ravel with axes
1 2 3 4
5 6 7 8
,[1.5]'ABC'
A
B
C
Dyadic Comma means
1 2 3 , 4 5 6
1 2 3 4 5 6
cube , 99
1 2 99
3 4 99
5 6 99
7 8 99
1 2 3 ,[0.5] 4 5 6 ⍝ Laminate
1 2 3
4 5 6