To cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
May 3, 2019 · War of the Spark
To counter a spell or ability means to cancel it, removing it from the stack. It doesn’t resolve and none of its effects occur. A countered spell is put into its owner’s graveyard.
January 25, 2019 · Ravnica Allegiance
To counter a spell or ability means to cancel it, removing it from the stack. It doesn't resolve and none of its effects occur. A countered spell is put into its owner's graveyard.
February 1, 2014 · Born of the Gods
To counter a spell or ability means to cancel it, removing it from the stack. It doesn’t resolve and none of its effects occur. A countered spell is put into its owner’s graveyard.
September 30, 2011 · Innistrad
To counter a spell or ability means to cancel it, removing it from the stack. It doesn't resolve and none of its effects occur. A countered spell is put into its owner's graveyard.
June 17, 2011 · Commander 2011
To counter a spell or ability means to cancel it, removing it from the stack. It doesn’t resolve
April 1, 2011 · Duel Decks: Knights vs. Dragons
To counter a spell or ability means to cancel it, removing it from the stack. It doesn't resolve and none of its effects occur. A countered spell is put into its owner's graveyard.
February 4, 2011 · Mirrodin Besieged
To counter a spell or ability means to cancel it, removing it from the stack. It doesn’t resolve and none of its effects occur. A countered spell is put into its owner’s graveyard.
October 1, 2010 · Scars of Mirrodin
To counter a spell or ability means to cancel it, removing it from the stack. It doesn’t resolve
February 1, 2010 · Worldwake
To counter a spell or ability means to cancel it, removing it from the stack. It doesn't resolve and none of its effects occur. A countered spell is put into its owner's graveyard.