Why is there "the" in the following sentence?

He invented THE slide rule.

They are not talking about a specific common noun. (Like in: There is only one blue car in the parking lot. Where is THE car?)

Thank you.


3 Answers 3


We use a definite article ('the')

(1) When the noun, singular or plural, proper or not, is specific, not arbitrary, and not new to the reader.

The hat on my head, the car in the garage, the meat on the plate, the wheels of the car, the king of England, the people in the shop, the birds in the tree.

We can use 'the' before proper nouns, mainly the names of people or places, if we wish to distinguish them from identically named others.

(a) In the UK, when discussing famous names (there is a famous movie star called Tom Cruise):

Person A: I am having lunch with Tom Cruise tomorrow.
Person B: What the Tom Cruise? [The movie star?]
Person A: No, someone else with the same name. He's an IT specialist.

In these cases, 'the' is pronounced, with emphasis, 'thee' (i.e. as if before a vowel sound, even if the name does not start with a vowel).

(b) to clarify who someone is, when they aren't famous, but probably known to both people:

Person A: I saw Ray Jones last week.
Person B: What, the Ray Jones who runs the auto repair shop?
Person A: Yes, that's him.

In these cases, 'the' may be pronounced, as in standard English, 'thee' before a vowel sound, and 'thuh' before a consonant sound.

2. When we intend a singular noun to refer to an entire class of items when we are speaking or writing generically.

This usage is particularly common with, but not restricted to, species of animals, inventions, or musical instruments. The horse is a useful animal; the lion is king of the jungle; the computer has changed the way we work; the violin is a hard instrument to learn.

  • Interestingly, in at least one dialect of English, 'the' is used for proper names e.g. "the JimmyJames". It sounds so strange to me but it sort of fits into #1, maybe.
    – JimmyJames
    Feb 27 at 21:35
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    @JimmyJames - yes, sometimes. In the UK, certainly, for clarification we can use 'the' (always pronounced 'thee' and emphasised in speech) about someone with a famous name, e.g. I am having lunch with Neil Young. What the Neil Young? No, he's a car dealer from Manchester. or spoken normally e.g. Do you know Ray Jones? Do you mean the Ray Jones who is the manager of the city library? Yes, that's him. But to say 'Joe, meet the Peter Wilson' or 'Take that letter to the Mary Brown' would be crazy and wrong in any dialect that I know of, except perhaps as a kind of joke. Feb 27 at 23:00
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    @MatthieuM. I proposed an edit that reintroduces quotes, but only for the "Person A: ... Person B:..." conversations. I now see that there was some discussion already on the use of quotes - if the edit makes it in and you dislike it, please blame me and not MichaelHarvey. Personally, I found it confusing to have the dialog interspersed with the commentary without quote sections to distinguish it as a hypothetical conversation between the two parties.
    – Blackhawk
    Feb 28 at 19:26
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    @Blackhawk - thank you for your helpful editing. I have often seen the 'quote' formatting used to set off self-written text that seems in need of visual separation, and have done it myself plenty of times, and no-one has complained before MatthieuM. Perhaps I am over-sensitive to criticism, but I then removed all the little > characters. I have in the past deleted answers that got even one downvote. Possibly I should have stuck to my guns? Feb 28 at 20:11
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    @Blackhawk: I think it's fine for the dialogue, as a way to set it apart visually, since it's clear from the context it's not a quote. Mar 1 at 7:49

I agree with Michael Harvey's answer. I'll add the following.

According to NASA (see link), the Wright brothers invented the aeroplane. This refers to a class of flying machine that was different from existing gliders, airships or hot-air balloons.

When we talk about the slide-rule, we mean the generic instrument as it was first conceived. However, we could say for example "John Smith invented a slide-rule. It had an inbuilt magnifying glass that made it easier to read." This is no longer representative of the whole class of slide rules - it is a particular type. Having mentioned it, we could of course go on to say "The John Smith slide-rule never met commercial success", or similar.

Link to NASA website (Who Invented the Aeroplane?) https://www.nasa.gov/audience/forstudents/k-4/home/F_Who_Invented_Aeroplane.html


Let's contrast all the possible variations that could be made:

1. He invented slide rule.

This would certainly be simple, and could be argued to make logical sense, but it's just ungrammatical. I don't know an objective reason why, it's just the way it is. This construction is only used with proper nouns, like

He invited Sly Rouge.

2. He invented a slide rule.

Chasly already discussed this. It is a possible sentence, but it means he invented a specific design of slide rule, not the basic concept common to all slide rules. So the sentence expresses something subtly, but significantly different.

3. He invented slide rules.

Same as in 2., this refers to particular designs, not the general invention. This time multiple of them.

4. He invented the slide rule.

The correct form, discussed in the accepted answer.

I'd note that the context could still cause this to change meaning from invention of the slide-rule-concept to something more specific, e.g.

She looked upon her father's desk and saw some pencils, a stapler, and an unusual kind of slide rule, like she had never seen before. Intrigued, she asked the secretary where it came from, but he could not say, remembering only to have purchased the stapler. She would later find out that her father had invented the slide rule himself.

In this case, “the slide rule” refers again to the single object.

5. He invented the slide rules.

I would say this is actually also correct and expresses almost exactly the same as 4., but has a different emphasis. It makes it explicit that there is a certain family of designs, suggesting in particular that there are only a limited number of variations, and that he covered them all with his invention.

  • I'm not sure why this is getting downvoted. It's helpful.
    – Tony Ennis
    Mar 1 at 21:19

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