"Ability" and "effect" are often confused with one another. An instruction in an object"s text is an ability. The result of following such an instruction is an effect. For more information, see section 4, "Spells, Abilities, and Effects."
When an activated ability is played, it goes onto the stack and stays there until it"s countered, it resolves, or it otherwise leaves the stack.
When an effect states that an object "gains" or "has" an ability, it"s granting that object an ability. If an effect defines a property of an object ("[card or permanent] is [property]"), it"s not granting an ability. For example, an Aura might read, "Enchanted creature is red." The Aura isn"t granting an ability of any kind; it"s simply changing the enchanted creature"s color to red.
Ability Word
An ability word appears in italics at the beginning of some abilities on cards. Ability words are similar to keywords in that they tie together cards that have similar functionality, but they have no special rules meaning and no individual entries in the Comprehensive Rules.
Activated Ability
An activated ability is written as "activation cost: effect." By paying the activation cost, a player may play such an ability whenever he or she has priority. See rule 403, "Activated Abilities."
Activation Cost
The activation cost of an activated ability is everything before the colon in "activation cost: effect." It must be paid to play the ability. See rule 403, "Activated Abilities."
Example: The activation cost of an ability that reads "{2}, {T}: You gain 1 life" is two mana of any color plus tapping the permanent.
Active Player
The active player is the player whose turn it is. The active player gets priority at the start of each phase or step (except for the untap and cleanup steps), after any spell or ability (except a mana ability) resolves, and after combat damage resolves. See rule 200.3.
Active Player, Nonactive Player Order
Whenever players are instructed to make choices at the same time, the active player makes all his or her choices first, then the nonactive players do so in turn order. This is called the "Active Player, Nonactive Player order" rule, or "APNAP order" rule. See rule 103.4. This rule is modified for Two-Headed Giant play; see rule 606.6d.
Active Team
In the Two-Headed Giant variant, the active team is the team whose turn it is. The active team gets priority at the start of each phase or step (except for the untap and cleanup steps), after any spell or ability (except a mana ability) resolves, and after combat damage resolves. See rule 200.3 and rule 606.6d.
Additional Cost
Some spells have additional costs listed in their text. These are paid at the same time the player pays the spell"s mana cost. See rule 409, "Playing Spells and Activated Abilities."
Affinity
Affinity is a static ability that functions while the spell is on the stack. "Affinity for [text]" means "This spell costs you {1} less to play for each [text] you control." The affinity ability reduces only generic mana costs. It doesn"t reduce how much colored mana you have to pay for a spell. It can"t reduce the cost to play a spell to less than 0. See rule 502.31, "Affinity."
Alternative Cost
The rules text of some spells reads, "You may [action] rather than pay [this object"s] mana cost," or includes the phrase, "you may play [this object] without paying its mana cost." These are alternative costs. Only one such alternative cost can be applied to any one spell. Other spells and abilities that ask for a spell"s mana cost still see the actual mana cost, not what was paid to play the spell. If an effect requires paying additional costs to play a spell, it still applies to the alternative cost. See rule 409, "Playing Spells and Activated Abilities."
Amplify
Amplify is a static ability. "Amplify N" means "As this object comes into play, reveal any number of cards from your hand that share a creature type with it. This permanent comes into play with N +1/+1 counters on it for each card revealed this way. You can"t reveal this card or any other cards that are coming into play at the same time as this card." See rule 502.27, "Amplify."
Ante (Obsolete)
Earlier versions of the Magic rules included an ante rule as a way of playing "for keeps." Playing Magic games for ante is now considered an optional variation on the game, and it is allowed only where it"s not forbidden by law or by other rules. Playing for ante is strictly forbidden under DCI tournament rules. When using the ante rule, each player puts one random card from his or her deck into his or her ante zone at the beginning of the game. At the end of the game, the winner becomes the owner of the cards in each player"s ante zone. See rule 217.9, "Ante."
APNAP Order
See Active Player, Nonactive Player Order.
Artifact
Artifact is a type. The active player may play artifacts during his or her main phase when the stack is empty. When an artifact spell resolves, its controller puts it into play under his or her control. See rule 212.2, "Artifacts."
Artifact Creature
An artifact creature is a combination of artifact and creature, and it"s subject to the rules for both. (See rule 212.2, "Artifacts.") Some artifact creatures don"t have a creature type. Those that do will say "Artifact Creature [creature type]"; for example, "Artifact Creature Golem." "Artifact" isn"t a creature type.
Artifact Land
An artifact land is a combination of artifact and land, and it"s subject to the rules for both. (See rule 212.2, "Artifacts.") Artifact lands can only be played as lands. They can"t be played as spells. Some artifact lands don"t have a land type. Those that do will say "Artifact Land [land type]."
Artifact Type