On the day of a Colleague's Birthday, I asked him "Which birthday" meaning to ask "How old have you become today". He was of the opinion that it is not a correct usage. Is the usage "Which Birthday" correct? If not what would be the right way (both I and my Colleague are not native English speakers)

2 Answers 2


I can see both points of view.

'Birthday' is used as shorthand for 'annual commemoration of your day of birth'.

In this sense, you could say it implies a choice of options, including, say, '33rd birthday', '50th birthday', '99th birthday', etc.

Strictly speaking, though, we can only ever have one birthday - the day on which we were born.

So, paradoxically, your 20th birthday (in the first sense) would actually be the 19th commemoration of your actual day of birth. Put that to someone born on 29th February, or Queen Elizabeth II, who has 2 birthday commemorations every year, and you're in even more murky natal waters.

  • 1
    Although I do not consciously remember it, I am quite sure that my first birthday was the first commemoration of my actual birth (which according to the records, took place one year earlier), making my 20th birthday the 20th event of the kind, not the 19th. If your actual day of birth was seen as a commemoration in itself, your 20th birthday is the 21st commemoration of the event, not the 19th.
    – oerkelens
    Feb 19, 2014 at 10:28
  • The dictionary defines birthday as the anniversary of one's birth, and that's also the common usage. The day of your actual birth is normally referred to as your birth date or date of birth.
    – nnnnnn
    Nov 8, 2019 at 12:34

While it could be argued that, "Which birthday?" is grammatically correct, a native speaker would generally ask, "How old are you?"

  • I think the reason people ask 'which birthday?', is that it sounds vaguely less impertinent than asking someone directly how old they are! Refreshingly, I find that the Japanese have no affectation about age, and can be quite direct in asking you how old you are? Indeed it can often be an early question when someone meets you for the first time. Add that to the fact that they venerate age, it can imagine it being pleasant to be around such people in ones advancing years!
    – WS2
    Feb 19, 2014 at 12:39
  • The culture here seems to have no age hangups either, if we exclude the media. I delight in the fact I survive another year - always worth a celebration, and I'm sure in years to come I'll be even more delighted.
    – Rory Alsop
    Feb 19, 2014 at 13:16
  • Where is 'here'?
    – WS2
    Feb 19, 2014 at 14:22
  • here is: Scotland :-)
    – Rory Alsop
    Feb 19, 2014 at 15:50
  • Are you saying it is the done thing in Scotland, to ask anyone you meet, when you are first introduced to them, how old they are?
    – WS2
    Feb 19, 2014 at 20:19

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