Vary With vs. Vary By – Which is Correct?
Both “vary with” and “vary by” are correct, but they express different relationships. Use “vary with” when one thing changes alongside another, often as conditions change. Use “vary by” when identifying the factor, amount, or category responsible for differences. Context determines the natural choice in each sentence in everyday writing.
Vary With or Vary By – Which is Correct?
Vary with and vary by are both correct English expressions, but they are not always interchangeable. Use vary with to show that one quantity changes in response to, or alongside, another changing condition. Use vary by to identify the basis, factor, amount, or category that explains the difference.
For example, “Prices vary with demand” means that prices change as demand changes. In contrast, “Prices vary by region” means that the prices are different from one region to another. The noun after with usually represents a changing influence, while the noun after by usually identifies a method of comparison or source of variation.
The Best Trick to Remember the Difference
Use the change-alongside test for vary with: if you can replace the phrase with “change as,” choose with. Use the category test for vary by: if you can replace the phrase with “differ according to” or “be different from one category to another,” choose by.
| Word | Part of Speech | Meaning | Example |
|---|---|---|---|
| vary with | Verb phrase | Change alongside or in response to something | Sleep needs vary with age. |
| vary by | Verb phrase | Differ according to a factor, amount, or category | The fee varies by location. |
How to Use Vary With
Use vary with when one thing changes in connection with another thing. The second noun typically describes a condition, influence, measurement, or circumstance that itself changes or affects the first subject. This construction is common in academic, scientific, technical, and professional writing, although it is also natural in everyday conversation.
The phrase often describes a relationship between two variables. It does not necessarily mean that one variable directly causes the other; it simply indicates that their values or conditions change together.
Example 1: The amount of sunlight varies with the season.
Example 2: A person’s calorie requirements may vary with activity level.
Example 3: The color of the leaves varies with the acidity of the soil.
What are the different forms of vary?
Vary is a regular verb. Its main forms are vary (base form), varies (third-person singular present), varied (past tense and past participle), and varying (present participle). For example: “Conditions vary,” “The result varies,” “The results varied,” and “The results are varying.”
Etymology of the word vary
Vary comes from the Latin verb variare, meaning “to change” or “to make different.” It entered English through Old French and has been used in English since the late Middle Ages. Its core meaning remains connected to difference, change, and lack of uniformity.
How to Use Vary By
Use vary by when you want to identify the factor used to compare different values, groups, places, times, or conditions. The phrase often introduces a category or measurement that explains how something differs. It is especially common with words such as location, region, age, country, size, amount, and provider.
Vary by can also indicate the amount of difference. For example, “The prices vary by $20” means that the prices differ from one another by an amount of $20. In this use, by introduces the measurement of variation rather than the category being compared.
Example 1: Admission prices vary by age group.
Example 2: Delivery times vary by destination.
Example 3: The two estimates vary by less than one percent.
What are the different forms of vary?
Vary remains a regular verb when used with by. Its forms are vary, varies, varied, and varying. For instance: “Rates vary by provider,” “The rate varies by provider,” “Rates varied by provider,” and “Rates are varying by provider.”
Etymology of the word vary
The verb vary derives from Latin variare, “to change” or “to diversify.” English adopted the word through French. The prepositions with and by later developed their own grammatical functions, allowing speakers to distinguish between changing alongside a condition and differing according to a category or amount.
Related Concepts
Understanding comparison, variables, and prepositional meaning makes the difference between vary with and vary by easier to recognize.
- Variables: A variable is a factor that can change. In “temperature varies with altitude,” temperature and altitude are both treated as changing measurements.
- Comparison: Comparison examines how items differ from one another. “Vary by” often introduces the category or measurement used for that comparison.
- Prepositions: Small words such as with and by express different relationships. With often signals connection or accompaniment, while by can identify a method, factor, or amount.
- Cause and correlation: “Vary with” may show that two conditions change together, but it does not always prove that one directly causes the other.
Examples from Media and Literature
Professional writers use both expressions to describe changing conditions and differences among groups. The following examples reflect common uses in journalism, science writing, fiction, and public information:
- News reporting: “The cost of housing varies by neighborhood.” Here, by neighborhood identifies the categories being compared.
- Weather coverage: “Rainfall varies with elevation.” Here, with elevation shows a relationship between two changing conditions.
- Travel writing: “Hotel rates vary by season and destination.” The sentence identifies the factors used to compare rates.
- Scientific writing: “The reaction rate varies with temperature.” The reaction rate changes as temperature changes.
- Fictional description: “Her mood varied with the weather.” The character’s mood changed alongside the weather.
Practice Exercises
Choose the correct word to complete each sentence: with or by.
- The price of the ticket varies _____ the distance traveled.
- Plant growth can vary _____ the amount of available sunlight.
- Insurance premiums vary _____ the driver’s age and location.
- The temperature varies _____ several degrees during the afternoon.
- People’s preferred communication styles vary _____ culture.
Answer Key
- by — The distance is the basis for comparing ticket prices.
- with — Plant growth changes alongside the amount of sunlight.
- by — Age and location identify the comparison factors.
- by — Several degrees indicates the amount of difference.
- with — Communication styles change in connection with culture.
Vary With Synonyms
| Synonym | Definition |
|---|---|
| Change with | Change as another condition changes |
| Respond to | Change in reaction to an influence or condition |
| Depend on | Be influenced or determined by something else |
| Fluctuate with | Rise and fall alongside another changing factor |
Vary By Synonyms
| Synonym | Definition |
|---|---|
| Differ according to | Be different depending on a particular factor |
| Differ by | Have a measurable or identifiable difference |
| Range by | Show different values across categories or conditions |
| Be dependent on | Be determined or influenced by a particular factor |
Frequently Asked Questions
Question 1: Is “vary with” or “vary by” correct?
Both are correct. Use vary with when something changes alongside another condition, and use vary by when identifying a comparison category, influencing factor, or amount of difference.
Question 2: What is the difference between “vary with age” and “vary by age”?
“Vary with age” means that something changes as people get older. “Vary by age” means that the information is divided into age groups or compared according to age. The two phrases can overlap, but their emphasis differs.
Question 3: Is “vary by” used for amounts?
Yes. In a sentence such as “The prices vary by $10,” by $10 identifies the amount of difference. “Vary by” can also introduce categories, as in “Prices vary by location.”
Conclusion
Vary with means “change alongside” or “change in response to,” while vary by means “differ according to” a factor, category, or amount. Remember the change-alongside test for with and the category-or-amount test for by. Pro Tip: Choosing the precise preposition makes professional writing clearer and strengthens your credibility.
