Why did the king go to the dentist?
To get his teeth crowned!
Why do we laugh (or groan) at jokes? It’s all about recognising that games are being played with language – and we understand this even if we can’t explain the linguistic process.
So what is going on in a joke? There are a number of linguistic tricks being played …
Homophones
Homophones are words that sound the same, but have different spellings. These are the core of many jokes.
Where can you learn to make ice-cream?
In Sundae school.
The joke depends on us recognising the collocation ‘Sunday School’ and the denotation of ‘school’ (a place of education), but the heart of the humour lies in the homophones: the proper noun Sunday (a day of the week) and the concrete noun sundae (a type of ice-cream).
Word formation
Jokes can play games with compound words, by creating linguistic parallels that can’t actually be found in a dictionary …
Why do seagulls fly over the sea rather than over the bay?
Because they don’t want to be called bagels.
The compound noun ‘baygull’ is created by mirroring the structure of seagull (from the concrete nouns ‘sea’ + ‘gull’). Humour then arises from the homophones: ‘baygull’ (a gull that flies over the bay) and bagel (food).
Semantic ambiguity
What has a pelican got in common with the Electric Company?
They both have large bills.
This joke plays on the ambiguity of the meaning of the plural concrete noun bills: it is both ‘the horny beak of a bird’ and ‘an itemised written statement of charges for goods delivered or services rendered’. The sound and spelling of these nouns is the same, but their etymological root is different: bill (duck’s beak) comes from the Old English ‘bile’ (1000); bill (statement of charges) comes from the Latin ‘bulla’ meaning ‘seal’ (1420).
Grammatical structure
What did Adam say the day before Christmas?
“It’s Christmas Eve!”
The play on words here is grammatical (linked to the function of words) as well as semantic (linked to the meaning of words). In the collocation ‘Christmas Eve’, the noun ‘eve’ is a shortened form of ‘evening’ – it is commonly used to describe the day before a religious or cultural festival (e.g. Hallowe’en).
Drawing on shared cultural knowledge, the joke creates a pun on the day and on the name of the biblical figure Eve, the traditional partner of Adam. In grammatical terms, this makes Eve a vocative (a word or phrase used to attract someone’s attention) – Adam is directly addressing Eve. A vocative would usually be separated from the rest of the sentence with a comma. It is omitted here to create ambiguity.
Subject specific shared knowledge
Two hydrogen atoms meet and one says to the other, “I’ve lost my electron.” The other says, “Are you sure?”. The first replies, “Yeah, I’m positive!”
Do you have to be a chemist to understand this joke? No, but it helps.
The joke is based on subject specific knowledge: a hydrogen atom has a single positively charged proton and a single negatively 
charged electron in the nucleus. This makes it an electrically neutral atom – the positive and the negative charges are balanced. If it were to lose its electron, a hydrogen atom would no longer be neutral, but positive.
This subject-specific knowledge (positive ‘charge’) is overlaid with the familiar conversational adjective (positive) used to assert an opinion emphatically. The humour is only apparent to an ‘insider’, someone who shares the same knowledge as the joke-teller.
And here are two for you to try …
Why did the boy take a pencil to bed?
To draw his curtains.
Why was the mummy so tense?
Sara Thorne English Language 