A pun is a ‘play on words’ – as you know, many words in English have two meanings (or more!) and when we say something that makes sense with both meanings, it’s called a pun and this can sometimes be quite funny. Here is another example of a joke based on a ‘pun’ to explain what I mean: “When the TV repairman got married the reception was excellent.” Here the pun is ‘reception’. You can read the sentence two ways because ‘reception’ has two meanings:
1) Reception to do with a TV – if a TV has bad reception it means the picture isn’t clear. If there is excellent reception then you can see the picture perfectly. (you can also use this reception to talk about your mobile phone)
2) Reception to do with a marriage – after a wedding ceremony, many people in the UK and other countries have a party with food and music. This is called the reception.
Please could you give more examples to this PUN?
THANKS IN ADVANCE.
So the syntax of the pun extends to the "once". In "once a king" the "once" is a subordinating conjunction, in "once a night" it is a pronoun [="on one occasion and no more"] introducing an adverbial phrase.