What’s the Plural of Diagnosis?

Last Updated June 22, 2025

Plural Nouns

Dalia Y

BA, MA, Phil. Grammarflex's initial initiator and contributor.

What’s the plural 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 reach a diagnosis by observing the signs and symptoms of a disease, condition, or injury.

👍🏼Usage Note

✓
The doctor provided a detailed diagnosis after the examination.

✓
Comparing several diagnoses helps determine the best treatment.

✗
The medical team reviewed the different possible diagnosis.

✗
Her first diagnoses was incorrect.

Diagnosis (pronounced dye-ahg-no-sis) is singular.
Diagnoses (pronounced dye-ahg-no-seez) is plural.

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
thesis	theses

Greek nouns in English

💡Study Tip

The plural of “diagnosis”: associate it with other words ending in “-sis” that change to “-ses” for the plural, like “analysis” becomes “analyses.”

Usage: Diagnosis/diagnoses

Examples of “diagnosis”	Examples of “diagnoses”
Petitt learned of the diagnosis in the mail that Christmas Eve. Only 35 percent of individuals with private insurance get treatment within a year of diagnosis. Confirmation of the diagnosis now takes just six hours. The emotional stress of a cancer diagnosis is huge, her husband expressed. After the procedure, Breuning received a diagnosis: lung cancer.	Initially, Alzheimer’s diagnoses were only given through brain autopsies after patients died. From the large number of facts obtained, a list of possible diagnoses can be determined, which are referred to as the differential diagnosis. Hippocrates was known to make diagnoses by tasting his patients’ urine and smelling their sweat. Sub-types of diagnoses include: clinical diagnosis, laboratory diagnosis, and radiology diagnosis. Greenstick fractures are common radiological diagnoses.

Examples of “diagnosis”

Examples of “diagnoses”

Petitt learned of the diagnosis in the mail that Christmas Eve.

Only 35 percent of individuals with private insurance get treatment within a year of diagnosis.

Confirmation of the diagnosis now takes just six hours.

The emotional stress of a cancer diagnosis is huge, her husband expressed.

After the procedure, Breuning received a diagnosis: lung cancer.

Initially, Alzheimer’s diagnoses were only given through brain autopsies after patients died.

From the large number of facts obtained, a list of possible diagnoses can be determined, which are referred to as the differential diagnosis.

Hippocrates was known to make diagnoses by tasting his patients’ urine and smelling their sweat.

Sub-types of diagnoses include: clinical diagnosis, laboratory diagnosis, and radiology diagnosis.

Greenstick fractures are common radiological diagnoses.

Synonyms & nearby words

Synonyms	Nearby Words
decision	finding
conclusion	result
judgment	opinion
resolution	assessment
determination	evaluation
verdict	report

Origin of the word diagnosis

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

Worksheet: Greek nouns

Question 1 of 10

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).

Citation: Yash, D. “What’s the Plural of Diagnosis?” Grammarflex. www.grammarflex.com/whats-the-plural-of-diagnosis/

Sources

Greek percentage in English Wikipedia: medical diagnosis Diagnosis, Oxford Learner’s Dictionary, accessed on October 11, 2023.
Harper, Douglas. “Etymology of diagnosis.” Online Etymology Dictionary, https://www.etymonline.com/word/diagnosis. Accessed 11 October 2023.