To get back or recover something that was lost, taken away, or given up.
From Old French regaaignier, from re- 'again' + gaaignier 'to gain' (of Germanic origin). The word entered English in the 14th century, maintaining its sense of recovering what was previously possessed.
The prefix 're-' in regain emphasizes the cyclical nature of loss and recovery that's fundamental to human experience. Psychologically, we often value regained things more highly than things we never lost - a phenomenon called the 'endowment effect.'
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