Ones vs. Once vs. One in English

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English learners are often confused by many similar words or phrases. One such challenge is the difference between one, once, and ones. Although looking similar, they can’t be interchangeable. In this article, you will learn the difference between these three words, their functions, and usage rules.

The main difference between one vs. ones

Ones vs once sound similar. One has a different pronunciation but seems to have the same meaning. However, all of these words are used for different purposes in the English language.

  1. Used as a numeral to represent a single item or unit. 
  2. Used as a pronoun to refer to a singular entity or to any unspecified individual in a general sense.
A pronoun that refers to a specific set of items, units, or individuals that have been previously mentioned or are understood from the context.An adverb meaning one time, at one point in the past or future, or used to express something happening for the first time.
Usage in SentencesAs a numeral: "I need one ticket, please." As a pronoun: "Give me that one, please."Of all the dresses, I prefer the red ones.

"I have been to London once."


FunctionMay function as a noun, pronoun, or adjective.Functions as a pronoun. It is used to avoid repeating the noun that has already been mentioned or is clearly understood from the context.

Functions as an adverb, modifying verbs, adjectives, or other adverbs to indicate when an action or event occurs.


Now you understand that ‘one,’ ‘once,’ and ‘ones’ definitions vary. These words are used for different purposes, so it’s vital to understand the rules.

Ones in a sentence

Repetitions can make speech boring. That is why, in most languages, people use pronouns. Being a plural form of “one,” the word “ones” is used as a pronoun to add clarity. However, it often confuses language learners. So, here are some examples for better understanding:

  • I prefer the chocolate cookies to the vanilla ones. (“ones” replaces the word “cookies”)
  • Among the laptops available, the ones with longer battery life are more expensive. (“ones” replaces the word “laptops”)

So, you should use ones in a sentence when you want to replace previously mentioned or implied plural nouns. There are some common mistakes associated with using ones:

  1. Confusing one’s vs ones. Ones is a plural pronoun that is used to replace a noun. One’s indicates possession.
    1. I like these ones bookshelf design the most (incorrect).
    2. I like this one's bookshelf design the most. (correct)
  2. Using "ones" when the noun hasn’t been mentioned in the conversation.
    1. In the store, I looked at the ones on sale. (incorrect)
    2. I had to buy a new pair of shoes. In the store, I looked at the ones on sale. (correct)

By familiarizing yourself with the common mistakes and following the rules, you will use “ones” correctly, enriching your English communication skills.

One in a sentence

In English, numerals indicate the quantity of units. However, the word ‘one’ may be used for more purposes. It can be an adjective, noun, or pronoun. There are some rules and tips to avoid in each case.

One as a noun

When "one" is used as a noun, it refers to a singular entity or concept. You will often face such usage in conversational English. Here are the cases when ‘one’ is used as a noun:

  • to indicate the first thing in a set of series (e.g. Episode One);
  • to refer to the size of clothes (e.g. He usually wears a one.);
  • to refer to a one-dollar bill (e.g., I was shocked when a waiter brought me one to pay.)

Pay attention to such usage of the word ‘one.’ Using it in conversations, you may show up as a proficient language learner, establishing better connections with interlocutors.


One as a pronoun

People often use one as a pronoun to avoid repetition and sound accurate. Such usage is very common for both formal and informal communication. Here are some examples:

  • If wishes to succeed, one must practice regularly.
  • To improve skills, one must learn every day.

While "one" as a pronoun adds a formal tone, overusing it in informal situations can sound pretentious or unnatural. Keep this in mind and use one as a pronoun in formal or academic settings, and choose more conversational pronouns like "you" or "they" in casual discourse.

One as an adjective

One as an adjective is the most common way to use this word. It specifies the quantity of nouns, indicating a single item.

  • She is looking for one specific book in the library.
  • Give me one latte, please.

Although the usage seems similar, there is one common mistake: speakers use “one” unnecessarily when it’s clear that the noun is single.

  • Please, hand me one pen from the desk. (redundancy)
  • Please hand me a pen (improved)
  • I just need one signature to complete the form. (redundancy)
  • I just need a signature to complete the form. (improved)

Such redundancies aren’t grammatical mistakes but conversational ones. Removing the word “one” when it’s already understood that the thing is singular makes your speech sound clear and natural.

Once in a sentence

“Once” doesn’t have complex rules of usage in English, but language learners often confuse it with “one” and “ones.” The main functions of “once” are indicating frequency, specific points in time, or changes in condition. Here are some examples:

  • I once met my favorite author at a book signing. (indicating frequency)
  • Once, in the year 2000, we witnessed a total solar eclipse. (specific point in time)
  • Once you submit your application, you cannot make any changes to it. (speaking about changes in condition)

The challenges that language learners usually face using “once” are as follows:

  1. Confusing “one’s” and “once.” As it was said before, “one’s” is used to indicate the possession. “Once” is never used for this purpose.
  2. Building incorrect structure in conditional sentences. In some cases, in conditional sentences, “once” may replace the word “if.” So, you have to follow the standard rules of building conditional sentences. For example:
    1. Once you will finish your homework, we can go out. (incorrect, because “will” shouldn’t be used in the subordinate clause.)
    2. Once you finish your homework, we can go out. (correct)

Remember that “once” has only three main functions in the English language. Practice using this word, and you will quickly understand its difference from “ones” and make progress in English.

Exploring Ones, Once, and One in English


For most of English learners it might be challenging to choose the correct word between one, ones or once. But mastering the rules above and doing some practical exercises, you will overcome this barrier.

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