Escalate is a static ability of modal spells (see rule 700.2) that functions while the spell with escalate is on the stack. “Escalate [cost]” means “For each mode you choose beyond the first as you cast this spell, you pay an additional [cost].” Paying a spell’s escalate cost follows the rules for paying additional costs in rules 601.2f–h.
May 3, 2019 · War of the Spark
Melee is a triggered ability. “Melee” means “Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked with a creature this combat.”
January 25, 2019 · Ravnica Allegiance
Melee is a triggered ability. "Melee" means "Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked with a creature this combat."
August 26, 2016 · Conspiracy: Take the Crown
Melee is a triggered ability. “Melee” means “Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked with a creature this combat.”