Frequency: The word is one of the 700 most common words in English.
1.
If something happens ~ a period of time or an event, it happens continuously, or happens several times between the beginning and end of that period or event.
Sandstorms are common ~ the Saudi Arabian winter...
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2.
If something develops ~ a period of time, it develops gradually from the beginning to the end of that period.
Wages have fallen by more than twenty percent ~ the past two months...
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3.
An event that happens ~ a period of time happens at some point or moment in that period.
During his visit, the Pope will also bless the new hospital.
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