It is because some of the card text wrote: "...If it trigger an ability.", please tell me...

What is the difference between "Card Ability" and "Card Effect"?

Is "Constant Effect" an ability? Is "Forced Effect" an ability? and Is "Keywords" an ability?

Thanks for reply...

The term "card effect" covers actions, forced and constant effects, and keywords (like counterstrike, not to be confused with traits, like knight). The term "ability" was only used on a handful of cards from the core set and first battlepack cycle, I think. It's synonymous. In all cases, you can just replace "ability" with "action" or "effect".

cchopman said:

Lukas has said they are pretty much interchangeable. I'm just curious which cards you are referring to though. Eatine Harbour, for example, has received errata already.

The card which I referred was:

CaC01 Longbeard Hunter
Action: When a unit enters play, attach this unit to it. This unit then counts as an Attachment support card

with the text “Destroy attached unit if it triggers an ability . Then, return this card to your hand.”

Thanks, Entropy42...