# The use of the definite article before cardinal numbers

A sentence from the test. "He boarded the number 30 bus and went to work".

Why do we need to use the definite article here before the cardinal number? I was taught 2 basic scenarios: I took bus number 30. I took the 30th bus.

Is this particular case an exception or a set phrase?

• The 30 bus is not the 30th in a sequence, or the bus with fleet member 30; it is a bus on route number 30, and it is usual to use either a definite ('the') or indefinite ('a') article before the phrase 'number 30 bus'. Commented Jun 24 at 6:49
• @MichaelHarvey I think your answer addresses the OP's core misunderstanding in a way I don't see covered in the others (at least not that simply and clearly). Commented Jun 24 at 14:46

This sentence is correct:

• He boarded the number 30 bus.

This sentence is also correct:

• He boarded bus number 30.

So your general understanding is correct regarding the definite article as used with cardinal numbers. But that's not what we have in the first sentence. Number 30 in the first example is an adjectival phrase describing the bus, so the refers to the bus, not the number. We are following here the same pattern as with other adjectives: He boarded the red bus; he boarded the dirty bus.

EDIT (further examples to hopefully make the answer clearer)

Compare these sentences:

1. I went on a holiday for 4 days.
2. On the 4th day of my holiday I went to the museum.
3. The 4 day holiday to the beach was a very relaxing time.
4. The quick holiday to the beach wasn't nearly long enough.

#1 and #2 illustrate the point that the OP makes. With cardinal numbers, leave out the. ("for the 4 days" would be wrong.) With ordinal numbers, include the. ("On 4th day of my holiday" would also be wrong.)

But #3 and #4 are examples of a completely different issue. in both cases the connects with holiday, not with any numbers that just coincidentally happen to be in a descriptive phrase about that holiday.

For example, I could rewrite sentence #3 like this: "The holiday (which was 4 days long) was very relaxing." The has nothing to do with the number and everything to do with the holiday. Furthermore, 4 in this rewrite now has no article in front of it, as you would expect.

• Thanks. If I understand you right, the presence of the word "number" before 30 + bus turns a mere cardinal number into an adjectival phrase, right? Commented Jun 24 at 6:49
• No. 30 is still a cardinal number, so that hasn't changed. The adjective or adjectival phrase is the set of words that describes something about the bus. "The red bus" - red is an adjective. "The red and blue bus" - red and blue is an adjectival phrase. "The number 30 bus" - number 30 is also an adjectival phrase. It means "The bus that is identified with the number 30 on it." Commented Jun 24 at 7:28
• "Bus number 30" may be grammatically correct, but it's not idiomatic. As Michael says, 30 is the number of the bus route and not the individual vehicle. Commented Jun 24 at 7:45
• @PeterKirkpatrick - it's fairly usual practice to hyphenate compound adjectives placed before the noun, so a four-mile run, a three-ton load, a large-scale disruption, a well-dressed person, a long-awaited letter, an oh-so-lovely cream cake, etc. Commented Jun 24 at 15:00
• Where I am, it's common to use just the article and the number: "I took the 25 to work." Note that this convention is for public transportation only. Where I am, we do NOT use the article for highways, so "There's a traffic jam on 45." not "There's a traffic jam on the 45." Commented Jun 24 at 19:25

"The number 30 bus" is a noun phrase, and nouns have articles.

The number actually denotes the number of the route that the bus is on, not the bus itself. Throughout the day, several buses may traverse the route numbered 30 and all can be referred to as "the number 30 bus". So the number of the route is added to the noun 'bus' to help identify it.

The definite article is used in a particularly idiomatic way when it comes to public transport. We say things like "I get the bus to work" to mean you use that specific mode of transport rather than a specific bus, so this might also be contributing to your misunderstanding of this.