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.”
May 3, 2019 · War of the Spark
Crew is an activated ability of Vehicle cards. “Crew N” means “Tap any number of untapped creatures you control with total power N or greater: This permanent becomes an artifact creature until end of turn.”
January 25, 2019 · Ravnica Allegiance
Crew is an activated ability of Vehicle cards. "Crew N" means "Tap any number of untapped creatures you control with total power N or greater: This permanent becomes an artifact creature until end of turn."
September 30, 2016 · Kaladesh
Crew is an activated ability of Vehicle cards. “Crew N” means “Tap any number of untapped creatures you control with total power N or greater: This permanent becomes an artifact creature until end of turn.”