Does copying a spell with fork count as casting that spell?

When you cast Fork (or any copy effect like Twincast or Reverberate), the copy is put directly onto the stack without being cast. According to CR 706.12, a copy of a spell is not cast — it is simply created on the stack. Casting a spell is a specific process defined in CR 601.2 that involves paying costs, making choices, and placing a card from a zone onto the stack. None of those steps occur when a copy is created.

This distinction matters for many triggered abilities and replacement effects. For example, a card that triggers "whenever you cast an instant or sorcery spell" will not trigger when you create a copy via Fork. The copy is an instant or sorcery on the stack, but it was never cast. Similarly, storm (CR 702.40) counts spells cast, so copies generated by storm itself do not add to that count.

The copy does behave like the original spell in most other respects — it has the same characteristics, targets can be changed (CR 706.12), and it resolves independently — but its origin is not a cast event.

Concrete example: Your opponent controls a Goblin Electromancer and you cast Lightning Bolt. You then Fork the Bolt. The Fork copy of Lightning Bolt is placed on the stack, but because it was not cast, Goblin Electromancer's cost-reduction ability never applied (it only applies when casting), and any "whenever you cast a spell" trigger on either side does not fire for the copy.

Key rules: CR 601.2 (casting a spell defined), CR 706.10–706.12 (copies of spells and permanents), and CR 702.40 (storm counts spells cast, not copies).