A card leaves the field when it is returned from the field to the hand or Extra Deck, sent from the field to the Graveyard, or banished. Cards that are used as Xyz Material for an Xyz Summon do not leave the field.
When a card is returned from the field to the Main Deck, it is not considered leaving the field.
Older card effects may use the term "removed from the field".
Any effect whose condition involves leaving the field will not activate if the card leaves while face-down.