Basis Plural Form: Rule, Examples, and Mistakes
The plural form of basis is bases (pronounced BAY-seez). This follows the standard rule for English nouns ending in -is, where the -is changes to -es in the plural. You use basis when talking about one foundation, principle, or starting point, and bases when talking about two or more. For example: “The basis of her argument was solid” (singular) versus “They examined the bases of several competing theories” (plural).
Quick Answer
Singular: basis
Plural: bases
Pronunciation of plural: /ˈbeɪ.siːz/ (BAY-seez)
Rule: Words ending in -is change to -es in the plural (like thesis → theses, crisis → crises).
Understanding the Rule
The word basis comes from Greek, and English has kept the Greek plural pattern for many academic and formal words ending in -is. This is not a random exception—it is a consistent rule that applies to dozens of words in business, science, and academic writing. When you learn the pattern for basis, you can apply it to other words like analysis (analyses), hypothesis (hypotheses), and diagnosis (diagnoses).
Why This Matters in Business Writing
In professional emails, reports, and presentations, using the correct plural form of basis shows attention to detail. A common mistake is writing “basises” or treating basis as an uncountable noun. Getting this right helps you sound more polished and credible, especially in formal contexts like quarterly reviews, strategy documents, or client proposals.
Comparison Table: Basis vs. Bases
| Form | Usage | Example |
|---|---|---|
| Basis (singular) | One foundation, principle, or starting point | The basis of our pricing model is cost-plus. |
| Bases (plural) | Two or more foundations, principles, or starting points | We reviewed the bases for all three investment decisions. |
| On a daily basis (singular) | Fixed phrase meaning “every day” | We update the report on a daily basis. |
| On a case-by-case basis (singular) | Fixed phrase meaning “individually” | Exceptions are handled on a case-by-case basis. |
Natural Examples in Business Contexts
Formal Written Contexts (Reports, Proposals, Emails)
- “The basis for our recommendation is the market analysis completed last quarter.”
- “We identified three separate bases for the cost variance: raw materials, labor, and shipping.”
- “On what basis did you select the vendor?”
- “The legal team examined the bases of all claims before drafting the response.”
Informal or Conversational Contexts (Meetings, Quick Updates)
- “What’s the basis for that number?”
- “We need to check the bases of those assumptions before we present.”
- “I’m working on a project basis for now.” (Here, basis is singular and part of a fixed phrase.)
Email Contexts
- Subject: Basis for Revised Timeline
“Dear Team, The basis for the revised timeline is the feedback from the client review.” - Subject: Bases for Quarterly Adjustments
“Hi all, Please find attached the bases for our quarterly adjustments. There are two main factors.”
Common Mistakes with “Basis” and “Bases”
Mistake 1: Using “Basises”
Incorrect: “We reviewed the basises of the argument.”
Correct: “We reviewed the bases of the argument.”
Why: English does not add -es to words ending in -is. The -is changes to -es directly.
Mistake 2: Using “Basis” as a Plural
Incorrect: “There are several basis for this decision.”
Correct: “There are several bases for this decision.”
Why: Basis is always singular. When you have more than one, you must use bases.
Mistake 3: Confusing “Bases” with “Basis” in Fixed Phrases
Incorrect: “We meet on a weekly bases.”
Correct: “We meet on a weekly basis.”
Why: The fixed phrase “on a [adjective] basis” always uses the singular form, even when talking about repeated actions.
Mistake 4: Mispronouncing the Plural
Incorrect: Saying “base-ez” (like the plural of base).
Correct: Saying “BAY-seez” (two syllables, with a long e sound at the end).
Why: The plural bases is pronounced differently from the plural of base (which is also spelled bases but pronounced “base-ez”). Context usually makes the meaning clear, but careful speakers distinguish them.
Better Alternatives and When to Use Them
Sometimes you can replace basis or bases with simpler words, depending on your audience and tone.
| Original Phrase | Alternative | When to Use |
|---|---|---|
| The basis of our decision | The reason for our decision | Informal conversation or simple emails |
| On a regular basis | Regularly | To sound more direct and less wordy |
| The bases of the argument | The foundations of the argument | When you want to avoid confusion with the plural of “base” |
| On a case-by-case basis | Individually | In casual updates or quick notes |
When to keep “basis” or “bases”: Use them in formal writing, legal documents, academic contexts, and any situation where precision matters. They are the standard terms in business English and are expected in professional reports.
Mini Practice: Check Your Understanding
Choose the correct form (basis or bases) for each sentence. Answers are below.
- The ______ for our budget forecast is last year’s actuals.
- We examined the ______ of three different pricing strategies.
- She works on a freelance ______.
- What are the ______ for your conclusion?
Answers
- basis (singular, one forecast)
- bases (plural, three strategies)
- basis (fixed phrase: “on a freelance basis”)
- bases (plural, more than one reason)
Frequently Asked Questions
1. Is “bases” the plural of both “base” and “basis”?
Yes, the word bases is the plural of both base (pronounced BAY-sez) and basis (pronounced BAY-seez). Context and pronunciation usually make the meaning clear. In writing, the surrounding words will tell you which one is intended.
2. Can I use “bases” as a verb?
Yes, bases is also the third-person singular form of the verb to base (e.g., “She bases her opinion on data”). This is a different word with a different pronunciation (BAY-sez). Be careful not to confuse it with the plural noun bases.
3. Is it ever correct to say “on a daily bases”?
No. The fixed phrase is always “on a daily basis” (singular). Using bases in this phrase is a common error. The same rule applies to all similar phrases: “on a weekly basis,” “on a regular basis,” “on a case-by-case basis.”
4. How do I remember the plural of “basis”?
Think of other -is words you already know: thesis becomes theses, crisis becomes crises, analysis becomes analyses. The pattern is consistent. If you remember one, you remember them all.
Summary
To use basis and bases correctly in your business writing:
- Use basis (singular) for one foundation, principle, or starting point.
- Use bases (plural) for two or more.
- Always use basis in fixed phrases like “on a daily basis.”
- Pronounce the plural bases as BAY-seez to distinguish it from the plural of base.
- Avoid the common errors “basises” and using basis as a plural.
For more help with similar patterns, visit our Plural Spelling Rules section or explore Confusing Plurals for other tricky word pairs. If you have questions about this guide, please see our FAQ or contact us.
