Occurrence/əˈkɜːrəns/ Definition 1 of 2Pro Tip 1/3Happening Once Use 'occurrence' when something happens only once or at a specific time. The occurrence of a solar eclipse can be predicted. Pro Tip 2/3Unique Situations It's perfect for events that are unique or noteworthy. The occurrence of a new comet fascinated astronomers. Pro Tip 3/3Not a Habit Don't use 'occurrence' for regular routines or habits. Missing the train was an unusual occurrence for her.