The Difference between “A/An” and “One” (Audio Reading Included)
- Alex
- 3 days ago
- 5 min read
Recommended level: A2 (pre-intermediate)
What is the difference between "I saw one dog" and "I saw a dog"? Both sentences use a determiner ("one" and "a") to point to a singular countable noun ("dog"), but the intended focus of each sentence is different. In the first case, you want to emphasize the number of dogs you saw--one. In the second case, you want to emphasize what you saw--a dog.
So, what can we conclude from this?
What is the Difference Between "A/An" and "One"?
"A" and "an" focus on classification. "One" focuses on number. "A" and "An" are never stressed because we care more about the class of person, place, or thing they describe. "One" is often stressed because we care more about the number of people, places, or things it describes. In short, "a" and "an" focus on what, and "one" focuses on how many.
For a better understanding of this, let's take a look at one of the most common usage errors that English learners make when they use "one." Look at this example:
Grammatically, there is nothing wrong with this sentence, but it does not carry the meaning that the speaker probably wishes to express. The speaker probably wants to say that they saw something interesting on their way to work. In this case, they want to say that they saw someone dancing on the sidewalk. The intended focus isn't on the number of people, but on what the speaker saw. The unspoken question that the person wants to answer is not, "How many people did you see dancing on the sidewalk?" The unspoken question is, "Who or what did you see dancing on the sidewalk?" We care about classification, not number. Therefore, the correct sentence is, "On my way to work, I saw a man dancing on the sidewalk."
"A/An" examples
Here are some other "a/an" examples in which we care about classification, not number:
"Why is there a giant bag on the table?" (We don't care about the number of giant bags on the table. We care about the fact that there is a giant bag on the table, period!)
"I don't own a TV." (This person wants to say that they do not have a TV. The focus is on what they don't have.)
"Make sure that you bring a water bottle for the hike." (What do you need to go hiking? You need a water bottle.)
"She needs a new laptop." (What does she need? She needs a new laptop.)
"I have never seen a koala bear in person." (What have I never seen in person? I have never seen a koala bear.)
Does that make more sense now? I hope so!
"One" examples
Now, let's look at some "one" examples in which we care about number, not classification:
"I usually drink one cup of coffee per day." (How many cups of coffee do I usually drink per day? I usually drink one cup of coffee per day.)
"I saw only one car on the road today." (How many cars did I see? Only one! I want to focus on the number because I usually see many more cars on the road.)
"He has one living grandparent." (How many living grandparents does he have? He has one.)
"We have one piece of bread left. Can you buy some more today?" (How many pieces of bread do we have left? Just one. We should buy more because soon we will have zero pieces of bread.)
"My phone battery is at one percent." (How much power does my phone battery have? Just one percent of battery power.)
I hope this is becoming clearer and clearer. Now, let's ask one more question before we finish reviewing this topic...
Are both possible sometimes?
Yes! However, the emphasis still changes depending on whether you use "a/an" or "one." Let's take a look at a few examples to illustrate this.
Example 1
"He's just a man." (Focus on classification)
"He's just one man." (Focus on number)
You might hear one of these examples in a dramatic film, or see it in a book. If someone says, "He's just a man," the speaker means that the person is mortal and capable of dying, or that he is at least capable of being defeated. If someone says, "He's just one man," the speaker means that, "He is just one person. He is not an army of people." One person is usually easier to defeat than many people.
Example 2
"Can you give me a good reason why I should believe you?" (Focus on classification)
"Can you give me one good reason why I should believe you?" (Focus on number)
In the first case, "a good reason," we care about the reason. We are asking, "Tell me why I should believe you." In the second case, "one good reason," we care about the number. We are emphasizing that we want to hear at least one good reason because we do not believe that the person is capable of giving us even one good reason.
Example 3
"I have a brother and two sisters." (Focus on classification)
"I have one brother and two sisters." (Focus on number)
When someone asks you if you have any brothers or sisters, and you have one brother, it is common to say you have "one brother" or "a brother." The only difference is the emphasis on class versus number. However, most people focus on class, "a brother," if they have one.
For the final two examples, we will focus on how "one" can be used as an overemphasis of "a" or "an."
Example 4
"There's a space left on the list."
"There's one space left on the list"
In this case, we still care about class versus number, but when we use "one," we emphasize that the list is almost full. In speaking, "a" and "an" are almost never stressed. However, in a case like this, the word "one" is stressed. There is only one space left! Not two. Not three. One!
Example 5
"I need a volunteer to help me."
"I need one volunteer to help me."
In this case, we are desperate for a volunteer. We just need one person to help us! By stressing "one," we are almost begging for someone to raise their hand and offer their time.
If you would like another example of this overemphasis of "one," you can actually go back to example 2, which also shows this usage.
That's it! How do you feel now? More confident? You should! Thank you for learning English with me today, and I hope that you will return to read more of my work in the future. Until then, if you would like to support what I do, please consider purchasing one of my books. Perhaps you would like a PDF, e-book, or physical version of Perfect English Questions (and How to Answer Them!). Until next time, thanks for clicking, and remember to keep practicing.
