Does a spell that copies a spell count as casting that spell?

When you copy a spell, the copy is placed directly onto the stack as a new object, but it is not cast. Casting a spell is a specific process defined in CR 601.1 that involves taking a card from a zone (usually your hand), paying costs, and following the full casting procedure. Copying skips all of that entirely.

CR 706.10 specifies that when a copy of a spell is created, it is placed on the stack and is not considered to have been cast. This means abilities that trigger on casting — such as 'whenever you cast a spell' — will not trigger from the copy. Similarly, effects that apply 'as you cast' a spell do not apply to copies.

One important consequence: cards with the keyword 'Flashback' or other alternative casting costs cannot be used when a copy is made, because no casting is happening. Additionally, 'cast from hand' or similar zone-specific conditions are never satisfied by a copy.

Concrete example: You cast Lightning Bolt and your opponent controls a creature with an ability that says 'Whenever an opponent casts an instant, draw a card.' You then use Twincast to copy the Lightning Bolt. Your opponent draws only one card (from the original cast), not two, because the Twincast copy was never cast.

Relevant rules: CR 601.1 (casting a spell defined), CR 706.10 (copies on the stack are not cast), CR 603.1 (triggered ability conditions must be met at time of event).