Plural of Optimum
“Optimum” can be a noun or an adjective. As a noun it has two dictionary-recorded plurals, “optima” and “optimums.” As an adjective before a noun—such as “optimum conditions”—it does not pluralize at all.
For the noun “optimum,” both “optima” and “optimums” are recorded plurals. The adjective “optimum” does not take a plural ending.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| one noun instance | an optimum | Use singular noun. |
| more than one noun instance | optima / optimums | Both recorded plurals. |
| adjective before plural noun | optimum conditions | The adjective stays unchanged. |
Quick tests
Plural-choice test
Is “optimum” functioning as a countable noun here?
If yes: Use “optima” or “optimums” for more than one.
If no: If it is an adjective, keep “optimum” unchanged.
Caveat: The form choice is partly a word-class decision; this guide does not rank the two noun plurals beyond the dictionary evidence.
Examples
The model has several local optima.
“Optima” is a recorded noun plural.
The tests produced different optimums.
“Optimums” is also recorded.
We tested the optimum conditions.
Adjectival “optimum” does not pluralize.
Further guidance
Core difference
If “optimum” is a noun meaning a best point/condition, use “optima” or “optimums” for more than one. If it modifies another noun, leave it unchanged.
Fast Test
Try removing the following noun: if “optimum” itself names the thing, it is a noun; if it modifies a noun, it is an adjective.
Usage Boundary
Do not add a plural ending to adjectival “optimum.”
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- OPTIMUM definition and meaning | Collins English Dictionary (opens in a new tab)HarperCollins Publishers · Collins records the noun optimum with plurals optima and optimums.