What Is the Plural of Diagnosis?
The plural of diagnosis is diagnoses. This follows the rule for many medical and academic words that come from Greek, where the singular ending -sis changes to -ses in the plural. So you say one diagnosis but two diagnoses.
Quick Answer
Singular: diagnosis
Plural: diagnoses
Pronunciation note: The plural is pronounced /daɪəɡˈnoʊsiːz/ (dye-ug-NOH-seez), with a clear eez sound at the end, not iss.
Why It Is Not “Diagnosises” or “Diagnosi”
Many learners try to add -es to make diagnosises, but that is incorrect. English borrowed diagnosis from Greek, and Greek words ending in -sis change the -sis to -ses in the plural. Other examples include crisis → crises, thesis → theses, and analysis → analyses. Once you know this pattern, you can apply it to many medical and academic terms.
Comparison Table: Singular vs. Plural of Diagnosis
| Singular | Plural | Example Sentence |
|---|---|---|
| diagnosis | diagnoses | The doctor made a diagnosis after reviewing the test results. |
| diagnosis | diagnoses | The hospital reported three diagnoses of the same condition this week. |
| diagnosis | diagnoses | Her initial diagnosis was later confirmed by a specialist. |
| diagnosis | diagnoses | We need to compare the diagnoses from different clinics. |
Natural Examples
Here are examples you might hear in a hospital, clinic, or everyday conversation. Notice how the plural diagnoses is used naturally.
- In a medical report: “The patient received two separate diagnoses: one for diabetes and one for hypertension.”
- In a conversation between doctors: “We reviewed all the diagnoses from the morning rounds, and none were life-threatening.”
- In an email to a colleague: “Could you send me the diagnoses for the three new patients? I need to update their charts.”
- In a patient’s question: “How many different diagnoses can a person have at the same time?”
- In a research paper: “The study examined over 200 diagnoses across five hospitals.”
Common Mistakes
Even advanced English speakers sometimes make errors with this word. Here are the most frequent mistakes and how to avoid them.
Mistake 1: Using “diagnosises”
Incorrect: The lab confirmed three diagnosises.
Correct: The lab confirmed three diagnoses.
Mistake 2: Using “diagnosi”
Incorrect: We have two diagnosi to consider.
Correct: We have two diagnoses to consider.
Mistake 3: Confusing “diagnosis” with “prognosis”
Incorrect: The prognosis was diabetes. (Prognosis means the likely outcome, not the identification of a disease.)
Correct: The diagnosis was diabetes. The prognosis was good with treatment.
Mistake 4: Using the singular verb with the plural form
Incorrect: The diagnoses is clear.
Correct: The diagnoses are clear.
Better Alternatives and When to Use Them
Sometimes you may want to avoid the plural diagnoses if it sounds too formal or if you are speaking with a patient who might not know the term. Here are some alternatives and the context for each.
- “Diagnostic results” – Use this in a formal report or when speaking to colleagues. Example: “We reviewed the diagnostic results for all patients.”
- “Findings” – A more general term that works in both formal and informal settings. Example: “The findings showed two different conditions.”
- “Conditions identified” – Clear and patient-friendly. Example: “The conditions identified were asthma and allergies.”
- “Medical opinions” – Useful when the diagnosis is not yet confirmed. Example: “We have two medical opinions, and they differ slightly.”
In everyday conversation, you can often rephrase to avoid the plural altogether. For example, instead of saying “We have three diagnoses,” you could say “We have identified three conditions.” This is especially helpful when speaking with patients or their families.
Formal vs. Informal Tone
The word diagnoses is neutral in tone, but it is more common in formal writing and professional speech. In informal conversation, people might say “diagnoses” less often and instead use phrases like “what the doctor found” or “the test results showed.”
- Formal (email to a specialist): “Please find attached the diagnoses for the patients under my care.”
- Informal (text to a friend): “The doctor found two things wrong with me. I don’t remember the names.”
- Neutral (conversation with a nurse): “How many diagnoses did you record for the new admission?”
If you are writing a medical report, an academic paper, or a professional email, use diagnoses confidently. If you are speaking casually, you can still use it, but be prepared to explain if the listener is not familiar with the term.
Mini Practice: 4 Questions
Test your understanding of the plural of diagnosis. Choose the correct option for each sentence.
- The doctor made a single ______ after the examination.
a) diagnoses
b) diagnosis
c) diagnosises
Answer: b) diagnosis - The clinic reported five different ______ last month.
a) diagnosis
b) diagnoses
c) diagnosi
Answer: b) diagnoses - All the ______ were reviewed by the senior consultant.
a) diagnosis
b) diagnosises
c) diagnoses
Answer: c) diagnoses - How many ______ can a patient receive in one visit?
a) diagnosis
b) diagnoses
c) diagnosises
Answer: b) diagnoses
Frequently Asked Questions
1. Is “diagnoses” the only correct plural?
Yes. In standard English, the only correct plural of diagnosis is diagnoses. You may occasionally see diagnosises in very informal writing, but it is not accepted in professional or academic contexts.
2. How do you pronounce “diagnoses”?
The plural diagnoses is pronounced /daɪəɡˈnoʊsiːz/. The last syllable sounds like sees or seize, not siss. Practice saying it slowly: dye-ug-NOH-seez.
3. Can I use “diagnosis” as both singular and plural?
No. Diagnosis is always singular. Using it as a plural is a common error. Always use diagnoses for more than one.
4. What about “diagnose” as a verb?
The verb diagnose is different. Its past tense is diagnosed, and it does not follow the same pattern. For example: “The doctor diagnosed the patient with two conditions.” Do not confuse the verb with the noun.
Final Tip
If you remember that diagnosis belongs to the -sis → -ses family, you will never make a mistake. Practice with other words like crisis → crises and analysis → analyses to reinforce the pattern. For more help with similar plural forms, visit our Common Plural Forms section. If you have further questions, check our FAQ or contact us.
