⍶ — Left operand

Argument. Keys: Alt-Minus a. Hanzi: 丙

In a defined operator, ⍶ denotes its left operand: function or subject.

apply←{⍶ ⍵} ⋄ -apply 3 ⍝ ¯3
add←{⍶+⍵} ⋄ 10 add 3 ⍝ 13

⍺ and ⍵ remain the derived function’s arguments.