Channel
Channel is an ability word indicating that a card may be discarded for an effect. It was introduced in Saviors of Kamigawa.
Channel is written "Channel -- {Cost}, Discard this card: {Effect}."
Channel was featured only on spirit creatures. Flavorwise, Channel represents spirits gathering all of their energy and using it for a one-time special effect. It has an interaction with Epic and Soulshift; Channel abilities are often similar to real spells, but you may play them after playing an Epic spell. Soulshift allows you to reuse Channeled cards.
Examples
Arashi, the Sky Asunder File:Mana3.gifFile:Manag.gifFile:Manag.gif
Legendary Creature-Spirit
5/5
File:Manax.gifFile:Manag.gif, {T}: Arashi, the Sky Asunder deals X damage to target creature with flying.
Channel -- File:Manax.gifFile:Manag.gifFile:Manag.gif, Discard Arashi: Arashi deals X damage to each creature with flying.