“Terminus” has two accepted plural forms: “terminuses” and the Latin-derived “termini.” Because both are established, this is a genuine competing-plural case rather than a simple add-s rule.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Both “terminuses” and “termini” are accepted plurals of “terminus.” Choose the form that fits your audience or house style, and keep it consistent within the same context.
Key details
Confusion Familycompeting plural forms
Rule Familynumber and classical plurals
Termsterminus, terminuses, termini
Variant ScopeBoth terminuses and termini are accepted plural forms.
Further guidance
Core difference
Use either “terminuses” or “termini” as the plural of “terminus”; both are documented.
Fast Test
If a publication or field consistently prefers classical plurals, “termini” may fit; otherwise “terminuses” is also standard.
Usage Boundary
Do not claim that one of the two accepted plurals is universally the only correct form.
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.
“Dogmas” is the ordinary English plural of “dogma,” while the classical plural “dogmata” is also recorded. The choice is therefore a genuine competing-plural question rather than a simple spelling variant.
Both “foci” and “focuses” are accepted plurals of “focus.” Do not assume the Latin-derived “foci” makes “focuses” incorrect; dictionaries record both forms.
Both “formulas” and “formulae” are accepted plurals of “formula.” Do not present “formulae” as the only correct plural or treat “formulas” as an error: both are dictionary-recorded forms.
“Forum” has two dictionary-recorded plurals: “forums” and “fora.” The regular plural is common in general use, while the Latin-derived plural survives especially in more formal or specialized contexts.
