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Are there any differences in their meanings?

He's at the supermarket VS. he's in the supermarket.

He's at the park VS. he's in the park

He's at the firehouse VS. he's in the firehouse.

He's at the house VS. he's in the house


Thanks in advance.

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future332Are there any differences in their meanings?

He could be outside in the first of each pair (with 'at'), but it is unlikely.