A cost is an action or payment necessary to take another action or to stop another action from taking place. To pay a cost, a player carries out the instructions specified by the spell, ability, or effect that contains that cost.
July 13, 2013 · Magic 2014
Each player begins the game with a starting life total of 20. Some variant games have different starting life totals.
July 16, 2010 · Magic 2011
Each player begins the game with a life total of 20.
February 1, 2010 · Worldwake
Objects can deal damage to creatures, planeswalkers, and players. This is generally detrimental to the object or player that receives that damage. An object that deals damage is the source of that damage.