This article is from the Magic: The Gathering Rules FAQ, by Patrik Linell (pls@claymore.nu) with numerous contributions by others.
A permanent is a card or token that's in play, and only one that's
in play. Cards in play are permanents, cards outside of play are not. Note
that instants and sorceries are never permanents, and neither are cards in
your hand, graveyard or library.
 
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