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.
What is the plural of “diagnosis”?
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.
Following Greek pluralization rules, the plural of diagnosis is diagnoses:
- Diagnosis (pronounced dye-ahg-no-sis) is singular,
- Diagnoses (pronounced dye-ahg-no-seaz) is plural.
As a noun, diagnosis is irregular (it doesn’t add “es”, but modifies its singular suffix by swapping the “-i” with “-e” to switch to plural).
| Sentence examples | |
| singular | They are waiting for the doctor’s diagnosis. |
| plural | They are using new methods of giving diagnoses. |
English Greek nouns
Diagnoses works different. The -es suffix is not simply added or glued to the tail end of the word; rather, the -es replaces the suffix of its singular noun form, and so effectively changes the spelling and pronunciation of the entire word from singular to plural.
| singular | plural |
| crisis | crises |
| diagnosis | diagnoses |
| oasis | oases |
| synopsis | synopses |
| thesis | theses |
Diagnosis is not the only Greek word in Modern English: crisis, analysis, oasis, synthesis, thesis, and nemesis all follow the same pluralization pattern.
Pro tip! An easy way to recall the plural/singular forms of nouns like crisis, diagnosis, analysis, oasis, and so on, is by remembering their Greek roots, and that Greek nouns swap to –es as a plural.
Greek makes up roughly 5% of the English language. Most English words come from the Germanic languages (Dutch, German, Old Norse, Old Frisian, and others). Still, other vocabulary is inherited from various countries and languages, and may likewise use irregular singular/plural forms.
Examples of “diagnosis” in sentences
Petitt learned of the diagnosis in the mail that Christmas Eve.
—Dominic Gates, Anchorage Daily News, 27 Oct. 2022
Only 35 percent of individuals with private insurance get treatment within a year of diagnosis.
—Sandhya Raman Cq-roll Call (tns), al, 19 Oct. 2022
Confirmation of the diagnosis now takes just six hours.
—Aporva Mandavilli, BostonGlobe.com, 6 Oct. 2022
The emotional stress of a cancer diagnosis is huge, her husband expressed.
—Rae Johnson, The Courier-Journal, 31 Aug. 2022
After the procedure, Breuning received a diagnosis: lung cancer.
—André-naquian Wheeler, Vogue, 24 Oct. 2022
The plural of “diagnosis,” associate it with other words ending in “-sis” that change to “-ses” for the plural, like “analysis” becomes “analyses.”.
Examples of “diagnoses” in sentences
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.
Diagnosis synonyms
- decision
- conclusion
- judgment
- resolution
- determination
- verdict
- finding
- opinion
- result
Learn about other nouns!
- What’s the plural of bison?
- What’s the plural of moose?
- What’s the plural of sheep?
- What’s the plural of ox?
- What’s the plural of cactus?
- What’s the plural of crisis?
- What’s the plural of hypothesis?
Work Sheet
What is the correct plural form of the word “diagnosis” according to Greek pluralization rules?
The blog post states that the singular form “diagnosis” is pronounced:
How is the plural of “diagnosis” formed according to the post?
Which of these words follows the same irregular pluralization pattern as “diagnosis”?
According to the blog post, a common mistake is using the plural form “diagnoses” in which situation?
Comparing several helps determine the best treatment.
The doctor provided a detailed after the examination.
The medical team reviewed the different possible .
Her first was incorrect.
They are using new methods of giving .
Frequently Asked Questions
What is the plural of “diagnosis”?
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How is “diagnoses” (plural) pronounced?
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Why is “diagnoses” spelled differently?
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How do I use diagnosis vs diagnoses?
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Are other words like diagnosis pluralized?
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Yash, D. "What’s the Plural of Diagnosis?." Grammarflex, Jun 3, 2025, https://www.grammarflex.com/whats-the-plural-of-diagnosis/.
Sources
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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.
