concatenate

From The K Language Wiki
Concatenate
x,y

The concatenate builtin concatenates its two arguments into a single unit, based on the type of the arguments.

If both x and y are dictionaries, the result is a dictionary, and otherwise the result is an array.

 1,2
1 2

1 2,"abc"
(1
 2
 "a"
 "b"
 "c")

(1 2!2 3),2 3!3 4
1 2 3!2 3 4