Magic: The Gathering Comprehensive Rules Changes - Core Set - Ninth Edition to Ravnica: City of Guilds

Old rule (Core Set - Ninth Edition)	New rule (Ravnica: City of Guilds)
Affinity [Click to view all changes.]
Affinity Affinity is a static ability that functions while the spell is on the stack. "Affinity [text]" means "This spell costs you {1} less to play for each [text] you control." The affinity ability only reduces 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."	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."

Old rule (Core Set - Ninth Edition)

New rule (Ravnica: City of Guilds)

Affinity

Affinity is a static ability that functions while the spell is on the stack. "Affinity [text]" means "This spell costs you {1} less to play for each [text] you control." The affinity ability only reduces 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."

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."