How to Use Diagnosis Plural (Diagnoses, Diagnoseses?)

What’s the meaning of diagnosis?

A diagnosis is the “recognition of a disease from its symptoms” or the “discovery or identification of the cause of an illness or a problem”. Doctors and other professionals arrive at diagnoses by observing the signs and symptoms of a disease, condition, or injury.

👍🏼 Examples: diagnosis vs. diagnoses

✓ The doctor has made an initial diagnosis.

✓ He completely disregarded her previous diagnoses.

diagnosis (pronounced dye-ahg-no-siss) is singular.
diagnoses (pronounced dye-ahg-no-seeze) is plural.

Greek plurals: diagnosis & diagnoses

As a noun, diagnosis is irregular (it doesn’t add “es”, but modifies its singular suffix by swapping the “-is” with “-es” to switch to plural).

Singular	Plural
crisis	crises
diagnosis	diagnoses
oasis	oases
synopsis	synopses

Greek nouns in English

Sentence examples: diagnosis & diagnoses

Noun: diagnosis	Example sentences
diagnosis (singular)	The doctor's diagnosis confirmed a mild concussion after the fall. Her final diagnosis came after a series of imaging tests. Receiving an early diagnosis improved his chances of recovery. The specialist offered a second opinion on the tentative diagnosis.
diagnoses (plural)	The patient's prior diagnoses were all noted in his medical record. Multiple diagnoses made the treatment plan more complex. Clinic staff reviewed the team's earlier diagnoses during the case conference.

Quotes from the media & literature, with diagnosis

The ‘Genera Piscium’ contains well-defined diagnoses of 45 genera.

—A. Günther, Introduction to Study of Fishes, 1880

[Swindlers] seem to possess, in an extraordinarily high degree, the power of diagnosis,—of telling what are the weak spots in the mind of the ordinary man.

—V. Luiselli, Spectator, 1892

The crows can form a pretty correct diagnosis upon the case of a sick camel.

—S. W. Baker, Nile Tributaries of Abyssinia, 1872

Then came the diagnosis—to wit a severe contusion and strain of right knee.

—H. S. Wilson, Alpine Ascents, 1878

Synonyms & nearby words

Synonyms for diagnosis

discovery verdict judgment finding identification recognition interpretation conclusion result prognosis pronouncement

Origin of the word diagnosis

Diagnosis comes from Greek διάγνωσις (diágnōsis), meaning “a distinguishing, discernment, decision,” from διαγιγνώσκειν (diagignóskein), “to distinguish, discern.”

FAQs

Q: What is the plural of “diagnosis”?

A: The plural of “diagnosis” is diagnoses. Following Greek rules, the singular suffix “-is” is swapped with “-es”. It’s an irregular noun.

Q: How is “diagnoses” (plural) pronounced?

A: The plural form “diagnoses” is pronounced “dye-ahg-no-seez”. The singular “diagnosis” is pronounced “dye-ahg-no-sis”, so the ending sound is different.

Q: Why is “diagnoses” spelled differently?

A: The spelling changes because “diagnosis” is a Greek noun. Like other Greek nouns, it doesn’t add “es” but replaces the singular suffix “-is” with “-es” to change to plural.

Q: How do I use diagnosis vs diagnoses?

A: Use “diagnosis” as singular (“a detailed diagnosis”) and “diagnoses” as plural (“several diagnoses”). Don’t use the singular form after plural words like “different possible”.

Q: Are other words like diagnosis pluralized?

A: Yes, other English nouns from Greek use this rule. They swap “-is” for “-es” in the plural. Examples include crisis (crises), analysis (analyses), oasis (oases), synthesis (syntheses), and thesis (theses).

Sources

Norgate, G. Le G., and Sayoni Basu. "Wilson, Henry Schütz (1824–1902), literary scholar." Oxford Dictionary of National Biography. September 23, 2004. Oxford University Press. Date of access 7 Sep. 2025,
“Verdict, N.” Oxford English Dictionary, Oxford UP, December 2024, https://doi.org/10.1093/OED/3704991196.

Yash, D. "How to Use Diagnosis Plural (Diagnoses, Diagnoseses?)." Grammarflex, Sep 11, 2025, https://grammarflex.com/diagnosis-plural/.