Monadic Down Arrow means

Split

      mat
1  2  3  4
5  6  7  8
9 10 11 12

      ↓ mat
┌───────┬───────┬──────────┐
│1 2 3 4│5 6 7 8│9 10 11 12│
└───────┴───────┴──────────┘

      ↓[1] mat
┌─────┬──────┬──────┬──────┐
│1 5 9│2 6 10│3 7 11│4 8 12│
└─────┴──────┴──────┴──────┘

Dyadic Down Arrow means

Drop

      4 ↓ 'Pineapple'
apple
      ¯5 ↓ 'Pineapple'
Pine
      1 ¯2 ↓ mat
5  6
9 10
      1 ↓ mat
5  6  7  8
9 10 11 12

Language Elements