Event

An event is any occurrence in a Magic game. Multiple events may occur simultaneously.

Events are most seen when considering triggered abilities, which are put onto the stack when an event matching their trigger occurs, or replacement and prevention effects, which substitute or alter specific types of events.

Rules

From the glossary of the Comprehensive Rules (June 7, 2024—Modern Horizons 3)

Event

Anything that happens in a game. See rule 700.1.

From the Comprehensive Rules (June 7, 2024—Modern Horizons 3)

• 700.1. Anything that happens in a game is an event. Multiple events may take place during the resolution of a spell or ability. The text of triggered abilities and replacement effects defines the event they’re looking for. One “happening” may be treated as a single event by one ability and as multiple events by another.

  Example: If an attacking creature is blocked by two creatures, this is one event for a triggered ability that reads “Whenever [this creature] becomes blocked” but two events for a triggered ability that reads “Whenever [this creature] becomes blocked by a creature.”