Define an "activated ability" - how does this differ from a triggered ability?
Activated Ability: A repeatable effect with the format [Cost]: [Effect] — cost, then a colon, then the effect (Rules 376–377). You choose when and whether to use it during your own Main Phase in an Open State (Rules 378, 381). It goes on the Chain like a spell without a card, creating a Closed State.
Triggered Ability: An effect that happens automatically when a condition is met — recognized by "When…", "At…", or "The [Nth] time…" (Rules 382–383). You don't choose when they activate (except "you may" triggers); the game puts them on the Chain as soon as their condition is fulfilled.
Key differences
| Activated | Triggered | |
|---|---|---|
| Initiative | You choose to activate | Condition triggers automatically |
| Timing | Your turn, Main Phase, Open State only (default) | Any turn, any state (Open or Closed), any phase |
| Format | [Cost]: [Effect] |
When/At/[Nth] time…, [Effect] |
| "You may" | Always optional (you decide to activate) | Optional only if the text says "you may" — otherwise mandatory |
Bottom line: Activated abilities are manual — you pay a cost for a benefit when you want it. Triggered abilities are automatic — the game fires them when the right event happens, whether you wanted it or not.