If an activated ability of an Elf card in your graveyard references the card it's printed on by name, treat Thranduil, the Elvenking's instance of that ability as though it referenced Thranduil by name instead.

If Thranduil, the Elvenking gains a set of linked activated abilities (for example, one ability that exiles a card and another that refers to the card "exiled with" the object), that link only lasts for as long as Thranduil has those abilities. If it loses the abilities and then regains them, the link is lost.

Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keyword abilities are activated abilities and will have colons in their reminder text.