§ 383.1 Core Rules PDF (officieel)

Triggered Abilities can usually be recognized by the word "when" followed by a game action or event; the word "at" followed by a point in time during the turn sequence; or the phrase “the [Nth] time” followed by a game action or event. Examples: "When you conquer here, you may spend a buff to draw 1." "At the end of your turn, ready 2 runes." “The first time I move each turn, you may ready something else that's exhausted.”