If
See Intervening "If" Clause.

Illegal Action
An action that violates the rules of the game and/or requirements or restrictions created by effects. See rule 720, "Handling Illegal Actions."

Illegal Target
A target that no longer exists or no longer meets the specifications stated by the spell or ability that’s targeting it. See rule 608.2b.

Illustration
A picture printed on the upper half of a card that has no effect on game play. See rule 203, "Illustration."

Illustration Credit
Information printed directly below the text box that has no effect on game play. See rule 212, "Information Below the Text Box."

Imprint
"Imprint" used to be a keyword ability. It is now an ability word and has no rules meaning. All cards printed with the imprint keyword have received errata in the Oracle card reference.

Improvise
A keyword ability that lets you tap artifacts rather than pay mana to cast a spell. See rule 702.125, "Improvise."

In Play (Obsolete)
An obsolete term for the battlefield. Cards that were printed with text that contain the phrases "in play,""from play,""into play," or the like are referring to the battlefield and have received errata in the Oracle card reference. See Battlefield.

In Response To
An instant spell that’s been cast, or an activated ability that’s been activated, while another spell or ability is on the stack has been cast or activated "in response to" the earlier spell or ability. See rule 116.7.

Independent
See Dependency.

Indestructible
A keyword ability that precludes a permanent from being destroyed. See rule 702.12.

Infect
A keyword ability that affects how an object deals damage to creatures and players. See rule 702.89, "Infect."

Ingest
A keyword ability that can exile the top card of a player’s library. See rule 702.114, "Ingest."

Instant
A card type. An instant is not a permanent. See rule 304, "Instants."

Instead
Effects that use the word "instead" are replacement effects. The word "instead" indicates what an event will be replaced with. See rule 614, "Replacement Effects."

Interrupt (Obsolete)
An obsolete card type. All cards printed with this card type are now instants. All abilities that, as printed, said a player could "play as an interrupt" can now be activated like any other activated abilities (unless they’re mana abilities, in which case they follow those rules instead). All relevant cards have been given errata in the Oracle card reference.

Intervening "If" Clause
A specially worded condition checked as a triggered ability would trigger and again as it would resolve. See rule 603.4

Intimidate
A keyword ability that restricts how a creature may be blocked. See rule 702.13, "Intimidate."

Investigate
A keyword action that creates a Clue artifact token. See rule 701.34, "Investigate."

Island
One of the five basic land types. Any land with this subtype has the ability ": Add to your mana pool." See rule 305.6.

Islandcycling
See Typecycling.

Islandhome (Obsolete)
An obsolete keyword ability that meant "This creature can’t attack unless defending player controls an Island" and "When you control no Islands, sacrifice this creature." Cards printed with this ability have been given errata in the Oracle card reference.

Islandwalk
See Landwalk.