frequent occurrences 频繁发生
rare occurrences 罕见事例
sudden occurrences 突然发生
natural occurrences 自然现象
A: How many occurrences of this phenomenon have you seen?
A：你见过几次这种现象？
B: I have noticed several occurrences in the last month.
B：我在上个月注意到了几次。
1) 发生，出现
2) 事件，事例
3) 发生的次数或频率
1. 发生；出现
2. 事件；事例
noun
1. The fact or frequency of something happening.
Synonym: instances, events, happenings