When to use good luck and congratulations?

For example, suppose someone says "I'm doing an exam", so we respond by saying "Good luck!"

Dictionaries say 'Congratulations is used when you want to congratulate somebody' so is it possible to use congratulations to wish instead of good luck in my example?

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    "Good luck" comes before their success - you are saying you hope they will succeed. "Congratulations" comes after the success is achieved, and you are saying that you observed their success and approve of it. – Adam Dec 31 '14 at 18:37
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    Also - this hypothetical someone should say either "I am taking an exam" or "I am taking exams." – Adam Dec 31 '14 at 18:38
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    Adding to what @Adam already said - you cannot congratulate someone for something they have yet to achieve, you can only wish them luck that they will achieve it. [btw, Br Eng would allow for 'do', even though 'take' is better] – gone fishin' again. Dec 31 '14 at 19:11
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    The dictionary definition describes congratulate as "saying that you are happy about their good luck or success". If someone says "I am doing an exam" you would only congratulate them if the fact that they are taking an exam represents some type of success or good luck. For example, if only a few people were allowed to take that exam because of some other criteria. – ColleenV Dec 31 '14 at 19:12
  • @Adam please write up your comment as an answer, so this StackExchange question will include a definitive answer. You may include information from other comments. – CoolHandLouis Dec 31 '14 at 19:16


The definition you referred to is Oxford Learners Dictionaries: congratulation: "1 congratulations [plural] a message congratulating somebody (= saying that you are happy about their good luck or success)."

  • "Congratulations" comes after the success is achieved, and you are saying that you observed their success or good luck and approve of it.

  • "Good luck" must come before their success - you are saying you hope they will succeed.

Congratulations and good luck!

You could congratulate someone for taking a prestigious exam, such as a bar exam, especially if the person was expressing a positive sentiment at the fact that they had finally reached this point:

  • Jane: "Hey Joe, guess what!"

    Joe: "What!"

    Jane: "I'm almost finished! Tomorrow I'm sitting for the bar exam!"

    Joe: "Congratulations!"

    (You might also say "Congratulations! And good luck!")

"Taking an exam" vs. "doing an exam"

While "I'm taking an exam" is much more common, there are other phrases that are acceptable or even preferred within certain dialects of English. Note the following Google N-Gram:

Google N-Gram Google N-Gram: do an exam,doing an exam,take an exam,taking an exam,sit an exam,sitting an exam,sit for an exam,sitting for an exam,have an exam,having an exam,got an exam

Some of these results have a different context, such as a doctor who says, "I'm doing an exam" is performing an exam on someone. However, there are instances of "doing an exam" referring to the same meaning as "taking an exam" within the exact same idiomatic scenario. (There are also some subtle cases in different scenarios that could influence usage.) It would be conservative to use the phrase "I'm taking an exam" unless the culture you're in uses a different idiomatic phrase.

Credit to @Adam and other commenters for ideas and content of this answer.


I am going to take the driving test tomorrow. Good Luck!

I have got a nice job in a bank. Good luck!

The phrase "good luck" is used when you wish somebody success in something he is going to do.

I have passed the driving test. Congratulations!

I have been promoted to Sales Manager. Congratulations!

I won the jackpot. Congratulations!

You say "congratulations" to somebody to tell him that you are pleased that he has achieved something or succeeded in.

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