What Is the Plural of Diagnosis? | Spelling & Examples

The plural of “diagnosis” is “diagnoses,” pronounced [dahy-uhg-noh-seez]. Because diagnosis is a Greek-origin noun, it follows Greek pluralization rules that change “-is” to “-es.”

Diagnoses vs. diagnosis

A diagnosis is the process of determining a disease based on its signs and symptoms. It’s used when there is a single instance of a medical problem.

Diagnoses is the plural form of diagnosis. Diagnoses can be used to describe multiple medical issues within the same patient or a single diagnosis given to multiple patients.

Distinguishing between diagnosis and diagnoses is crucially important for accurate communication in the field of medicine, where multiple medical issues may be under consideration.

What are irregular plurals?

Some people wonder why the plural of “diagnosis” isn’t “diagnosises.” Diagnosis is considered an irregular plural, which deviates from the standard rules of pluralization in English.

Regular plural nouns can typically be made plural by simply adding “-s” or “-es” to the end of a word (e.g., dog/dogs and class/classes).

Some nouns, however, like diagnosis, follow different rules due to their Latin or Greek origins. Words of Greek and Latin origin are made plural by changing the “-is” to “-es” (e.g., diagnosis/diagnoses, axis/axes, and crisis/crises).

There are other irregular plurals that come from other origins, like Old English or other linguistic origins.

There’s another type of irregular plural called zero plurals. A zero plural is a word that remains the same in both the singular and plural forms.

Frequently asked questions

Why is the plural of “diagnosis” not “diagnosises”?

The plural of diagnosis is diagnoses, not diagnosises. Diagnoses is considered an irregular plural, which doesn’t follow the pluralization rules of regular plural nouns.

Diagnosis is a Greek-derived word, meaning it follows the Greek rules of pluralization, so the “-is” is changed to “-es.”

Scribbr’s free Grammar Checker can help you make sure you’re using the correct plural forms of words.

Is diagnosis plural?

Diagnosis is the singular form. The plural of diagnosis is diagnoses.

Diagnosis is not a zero plural noun, which is a word that remains the same in both the singular and plural forms. Diagnosis is a Greek-derived word that changes the “-is” in the singular to “-es” in the plural.

Scribbr’s Grammar Checker can help you fix errors with plural forms in your writing.

What is the plural of “crisis”?

The plural of “crisis” is “crises.” It’s a loanword from Latin and retains its original Latin plural noun form (similar to “analyses” and “bases”). It’s wrong to write “crisises.”

For example, you might write “Several crises destabilized the regime.”