Definition of believe in
1 : to have faith or confidence in the existence of (something) <Do you believe in ghosts?>
2 : to have trust in the goodness or value of (something) <She believes in (the value of) regular exercise.> <I believe in working hard to achieve success.> <She doesn't believe in using pesticides.>
3 : to have trust in the goodness or ability of (someone) <Despite his problems, his parents still believe in him.>
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