noun
1
BAD : Congratulations! You must be feeling very proud.
GOOD : Congratulations! You must be feeling very proud.
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Congratulations is a plural noun: 'Many congratulations to you both. I'm sure you'll be very happy together.' 'Give them our congratulations and say that we'll be getting in touch soon.'
2
BAD : Congratulations for your splendid examination results!
GOOD : Congratulations on your splendid examination results!
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congratulations on ( doing ) sth (NOT for ): 'Congratulations on your promotion. You certainly deserve it.'