بوابة الثانوية العامة المصرية

بسم الله الرحمن الرحيم
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She represented on behalf of her father who wasn't at the party
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to "speak on behalf of a person or entity" is to "speak on their side or part as their explicitly or implicitly delegated representative."
On behalf of the mayor, I declare this to be our city's fix-up and paint-up day.
To "speak in behalf of a person or entity" is to "speak in their interest, favor, or aid, without explicit deputization, and especially if they are unable to speak for themselves."
to plead in behalf of a cause.
the source WIKTIONARY
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