Spell

In Magic: The Gathering, the term spell has three meanings; one technical, one casual and one flavorful.

Technical
A spell is any card that has been played and thus placed on the stack. A card is only a spell when it is on the stack.

Spell ability
Any text on an instant or sorcery spell is a spell ability unless it's an activated ability, a triggered ability or a static ability. undefined undefined

Casual
Except for land, all of the original basic kind of card (summons, enchantments, sorceries, instants, interrupts and artifacts) are spells from the time they are cast until they resolve. However, non-permanents are collectively referred to as "spells" in common language. This includes sorceries and instants, along with the obsoleted mana sources and interrupts. This is because, under normal circumstances, these types of cards never exist in play except while they're on the stack.

Flavor
In the storyline, spells are the effect of a ritual that involves mental activity and a varying amount of both physical activity and the channeling of mana.

Mages use many different practices to channel mana, including chants, screams, and ritual motion. The concept of magic, unlike physics, has no unbreakable laws ; spellcasters can use their spell do virtually anything.