What is imprinting (Twilight series)?

Imprinting is a special trait of the werewolves in the Twilight series. What happens is a werewolf merely has to see the person their meant to imprint on and as Jacob says in Breaking Dawn "Bada bing, bada boom" that person is madly in love. Also in the beginning of the story, imprinting was rare and only two wolves had imprinted. By the end of Breaking Dawn 5 of the pack had imprinted, which led the pack to the conclusion that imprinting wasn't as rare as everyone thought.