con‧grat‧u‧la‧tion S3 /kənˌɡrætʃəˈleɪʃən, kənˌɡrætʃʊˈleɪʃən/ noun

1. congratulations
a) used when you want to congratulate someone:
‘I’ve just passed my driving test!’ ‘Congratulations!’
congratulations on
Congratulations on a superb performance!
b) words saying you are happy that someone has achieved something:
Give Oscar my congratulations.

2. [uncountable] when you tell someone that you are happy because they have achieved something or because something nice has happened to them:
letters of congratulation

[TahlilGaran] Dictionary of Contemporary English ▲

congratulation
noun
1.
BAD: Congratulations! You must be feeling very proud.
GOOD: Congratulations! You must be feeling very proud.

Usage Note:
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.'

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2.
BAD: Congratulations for your splendid examination results!
GOOD: Congratulations on your splendid examination results!

Usage Note:
congratulations on (doing ) sth (NOT for ): 'Congratulations on your promotion. You certainly deserve it.'

[TahlilGaran] Dictionary of Common Errors ▲