Common Mistakes with the Plural of Prognosis

If you are learning medical English, you have likely seen the word prognosis and wondered what its plural is. The direct answer is that the correct plural of prognosis is prognoses. This follows the rule for many Greek-derived nouns ending in -sis, where the ending changes to -ses. Using prognosises or prognosis as a plural are common errors. This guide will explain the rule, show you how to use it correctly in writing and conversation, and help you avoid the mistakes that even native speakers sometimes make.

Quick Answer: Prognosis Plural

• Singular: prognosis
• Plural: prognoses
• Incorrect forms: prognosises, prognosis (as plural)
• Pronunciation: prog-NO-sis (singular) / prog-NO-seez (plural)

When you need to talk about more than one medical forecast, always use prognoses.

Why the Plural Is “Prognoses”

The word prognosis comes from Greek, where nouns ending in -sis form their plural by changing the ending to -ses. This is the same pattern you see with other medical terms like diagnosis (plural: diagnoses), analysis (plural: analyses), and hypothesis (plural: hypotheses). English has kept this rule for these specialized words, so you cannot simply add an -es or -s to the end.

Comparison Table: Singular vs. Plural

Notice the pattern: the -sis becomes -ses. This is not a random exception; it is a consistent rule for this word family.

Formal vs. Informal Tone and Context

In formal medical writing, such as research papers, patient reports, or academic presentations, you must use prognoses correctly. Using the wrong plural can make you look unprofessional or careless. In informal conversation, such as talking with colleagues in a break room, you might hear someone say prognosises as a slip, but it is still considered incorrect. If you are writing an email to a doctor or a supervisor, always use prognoses. In everyday conversation with friends or family, you can still use the correct form; it sounds natural once you are used to it.

Nuance in Usage

There is a subtle nuance: prognosis can sometimes be used in a non-medical sense to mean a forecast or prediction about any situation. For example, “The prognosis for the project is not good.” In these cases, the plural prognoses is still correct when referring to multiple forecasts. However, this usage is less common than the medical one.

Natural Examples

Here are examples of how prognoses is used in real contexts.

Medical Writing (Formal)

• “The study compared the prognoses for patients who received early treatment versus those who did not.”
• “All prognoses were reviewed by a second specialist before being shared with the families.”
• “The doctor documented three different prognoses based on the patient’s response to therapy.”

Email Context (Professional)

• “Dear Dr. Lee, I have attached the latest prognoses for the patients in the oncology unit. Please review and confirm.”
• “Thank you for providing the prognoses for the clinical trial participants. We will update the records accordingly.”

Conversation (Informal)

• “The team discussed the prognoses for the new cases this morning. Most of them look hopeful.”
• “I heard the prognoses for the two surgeries were very different. One was much better than the other.”

Non-Medical Use

• “The economic prognoses from the analysts were all pessimistic for the next quarter.”
• “We received several prognoses about the election results, but none were accurate.”

Common Mistakes

Here are the most frequent errors learners and even native speakers make with the plural of prognosis.

Mistake 1: Adding “-es” to Make “Prognosises”

This is the most common error. Because most English nouns form their plural by adding -s or -es, people naturally try to do the same with prognosis. However, because it is a Greek loanword, it follows a different rule.

Incorrect: “The doctors gave three different prognosises.”
Correct: “The doctors gave three different prognoses.”

Mistake 2: Using “Prognosis” as Both Singular and Plural

Some people treat prognosis like sheep or deer, which have the same form for singular and plural. This is not correct for this word.

Incorrect: “We reviewed all the prognosis for the patients.”
Correct: “We reviewed all the prognoses for the patients.”

Mistake 3: Confusing “Prognosis” with “Diagnosis”

While both words follow the same plural rule, people sometimes mix up the meanings. A diagnosis identifies a condition, while a prognosis predicts the likely outcome. The plural forms are diagnoses and prognoses.

Incorrect: “The patient received two different diagnoses for the same illness.” (This is actually correct if they got two different identifications, but it is often confused with prognoses.)
Correct context: “The patient received two different prognoses about recovery time.”

Better Alternatives and When to Use Them

Sometimes, you might want to avoid the plural form altogether if you are unsure. Here are some alternatives that can work in specific contexts.

• “Outcome predictions” – Use this in formal writing when you want to be very clear. Example: “The outcome predictions for the patients varied.”
• “Forecasts” – This works well in non-medical contexts. Example: “The economic forecasts were revised.”
• “Expected results” – A simple alternative for general conversation. Example: “The expected results for the treatments were discussed.”

However, if you are in a medical setting, it is best to learn and use prognoses correctly. It is the precise term that professionals expect.

Mini Practice Section

Test your understanding with these four questions. Choose the correct option.

Question 1

Which sentence is correct?

A) The doctor shared the prognosises with the team.
B) The doctor shared the prognoses with the team.
C) The doctor shared the prognosis with the team. (Talking about one)

Answer: B is correct for plural. C is correct only if there is one prognosis.

Question 2

Fill in the blank: “The study analyzed the ______ of fifty patients over five years.”

A) prognosises
B) prognoses
C) prognosis

Answer: B. The study analyzed multiple patients, so the plural is needed.

Question 3

Is this sentence correct? “We have three different prognosis for the same condition.”

A) Yes
B) No

Answer: B. It should be “three different prognoses.”

Question 4

Which word follows the same plural rule as prognosis?

A) Virus
B) Diagnosis
C) Status

Answer: B. Diagnosis changes to diagnoses.

Frequently Asked Questions (FAQ)

1. Is “prognosises” ever acceptable in English?

No. “Prognosises” is not a standard English word. It is a common mistake, but it is not accepted in formal or professional writing. Always use “prognoses.”

2. Can I use “prognosis” as a plural in informal speech?

You might hear some people do this, but it is not grammatically correct. Even in casual conversation, using “prognoses” is clearer and shows you know the correct form. It is better to practice the correct plural.

3. How do I pronounce “prognoses”?

The singular “prognosis” is pronounced prog-NO-sis. The plural “prognoses” is pronounced prog-NO-seez. The last syllable changes from “sis” to “seez.”

4. What is the difference between “prognosis” and “diagnosis” in plural form?

Both follow the same rule: “diagnosis” becomes “diagnoses,” and “prognosis” becomes “prognoses.” The difference is in meaning. A diagnosis identifies a disease or condition. A prognosis predicts the likely course or outcome of that condition. For example, a doctor might give a diagnosis of diabetes and then a prognosis about how the patient will respond to treatment.

For more help with similar words, visit our Confusing Plurals section. You can also check our Common Plural Forms for other patterns. If you have further questions, please see our FAQ page or contact us.