Ampersand &
Ampersand is a Monadic operator with an ambivalent operand
Operator Ampersand means

Spawn

      delay←{'Delayed: ',⎕DL ⍵}    ⍝ delay function

      delay 10    ⍝ delay for 10 seconds
Delayed:  10.2228

      ⎕←delay&10  ⍝ delay for 10 seconds in new thread 1
1

      2+3 4       ⍝ execute something in current thread
5 6
                  ⍝ thread 1 completes:
Delayed:  10.03183

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