Conditional Passive Abilities can be recognized by the occurrence of "if" or "while" as part of the statement of the ability. Example: "While I'm attacking or defending alone, I have +2 [M]." Example: "If an opponent controls a battlefield, I enter ready."
§ 364.3.a Core Rules PDF (officieel)
§ 364 Conditions, rules, constraints, or statements that affect the course of regular play.
§ 364.3 Passive Abilities can be conditional.