What Is the Plural of Basis?
The plural of basis is bases (pronounced BAY-seez). This word follows a small group of English nouns that change their ending from -is to -es in the plural, a pattern borrowed from Greek. You use basis for one foundation, principle, or starting point, and bases for two or more of them. This guide explains the rule, gives you natural examples, shows common mistakes, and helps you use both forms correctly in academic and professional writing.
Quick Answer
| Form | Usage | Example |
|---|---|---|
| Basis (singular) | One foundation, principle, or reason | The basis of her argument is solid. |
| Bases (plural) | Two or more foundations, principles, or reasons | The report examines several bases for the decision. |
Remember: bases is also the plural of base (pronounced BAY-siz), but in academic writing, bases (BAY-seez) almost always refers to multiple basis.
Why the Plural Is “Bases”
English borrowed basis directly from Latin, which took it from Greek basis (step, pedestal). In Greek, nouns ending in -is form the plural by changing to -es. Other common words that follow this pattern include:
- crisis → crises
- thesis → theses
- hypothesis → hypotheses
- analysis → analyses
- diagnosis → diagnoses
This is not a regular English plural (which would add -es to make basis → basises). That form is incorrect. Stick with bases.
Comparison Table: Basis vs. Bases
| Context | Singular (Basis) | Plural (Bases) |
|---|---|---|
| Academic writing | The basis of the theory is empirical evidence. | Several theoretical bases support this model. |
| Business email | We need a clear basis for the budget. | Please list the bases for your cost estimates. |
| Everyday conversation | What is the basis of your opinion? | They have different bases for their choices. |
| Formal report | The study provides a solid basis for policy change. | The report identifies three bases for the recommendation. |
Natural Examples
Singular: Basis
- The basis of the contract is mutual trust.
- Her argument has no logical basis.
- We meet on a weekly basis to review progress.
- The basis for the new law is public safety.
Plural: Bases
- The researchers examined the theoretical bases of the experiment.
- There are multiple bases for the company’s decision to expand.
- These two proposals have different philosophical bases.
- The professor asked us to identify the bases of the author’s claims.
Common Mistakes
Mistake 1: Using “Basises”
Incorrect: The report lists several basises for the change.
Correct: The report lists several bases for the change.
Mistake 2: Confusing “Bases” with “Base”
Bases (BAY-seez) is the plural of basis. Base (BAY-s) is a different word meaning a bottom support or a military installation. Its plural is bases (BAY-siz). In writing, context tells you which one is meant.
Example of confusion: “The army has several bases in the region.” (Here bases is pronounced BAY-siz and means military camps.)
Example of correct academic use: “The study has several theoretical bases.” (Here bases is pronounced BAY-seez and means foundations.)
Mistake 3: Using Singular “Basis” When Plural Is Needed
Incorrect: The policy has many basis for its justification.
Correct: The policy has many bases for its justification.
Better Alternatives and When to Use Them
Sometimes you can replace basis or bases with a clearer word, depending on the context.
| Original | Alternative | When to Use |
|---|---|---|
| Basis of the argument | Foundation of the argument | When you want a more concrete image |
| Bases for the decision | Reasons for the decision | In everyday conversation or informal email |
| Theoretical basis | Theoretical framework | In academic writing for a more precise term |
| On a regular basis | Regularly | To sound more natural and less formal |
When to use it: Use basis and bases in formal, academic, or professional writing where precision matters. In casual conversation, reason or foundation often works better.
Formal vs. Informal Tone
Formal (academic or business email):
“The committee evaluated the bases for the proposed changes before reaching a conclusion.”
Informal (conversation or quick note):
“What’s the basis for your idea? Just curious.”
In formal writing, you will often see basis and bases used with words like theoretical, empirical, logical, or rational. In informal settings, people tend to use simpler phrases like reason or starting point.
Mini Practice: Check Your Understanding
Choose the correct form (basis or bases) for each sentence.
- The _____ of the study is a survey of 500 participants.
- There are several _____ for the company’s new policy.
- Her argument lacks a solid _____ .
- The researchers compared the theoretical _____ of both models.
Answers:
- basis
- bases
- basis
- bases
FAQ: Common Questions About the Plural of Basis
1. Is “bases” the plural of both “basis” and “base”?
Yes, but the pronunciation differs. For basis, the plural bases is pronounced BAY-seez. For base, the plural bases is pronounced BAY-siz. Context and pronunciation in speech make the meaning clear.
2. Can I use “basis” in a plural sense?
No. Basis is always singular. If you need to refer to more than one, use bases.
3. Is “on a daily basis” correct?
Yes. This is a common fixed expression meaning “every day.” It is perfectly correct in both formal and informal English.
4. What is the plural of “basis” in British English?
The same as in American English: bases. There is no difference. The spelling and pronunciation are identical in both major varieties of English.
Final Tip for Learners
If you are unsure whether to use basis or bases, ask yourself: “Am I talking about one foundation or more than one?” If it is one, use basis. If it is two or more, use bases. Practice with the examples above, and soon the choice will feel natural. For more help with tricky plural forms, explore our Common Plural Forms section or visit our FAQ page for additional questions.
