What’s the Plural of Diagnosis: Understanding Medical Terminology

• The plural of “diagnosis” follows Greek-origin rules, changing ‘-is’ to ‘-es’ to become “diagnoses.”
• Correctly applying “diagnosis” and “diagnoses” is vital for clear communication in medical and scientific contexts.
• “Diagnosis” is used for a single case; “diagnoses” is used for multiple cases.

When using the term in sentences, “diagnosis” refers to the identification of a disease or condition, while “diagnoses” is applied when referring to several determinations. It is important to use these terms correctly to maintain the accuracy and professionalism of medical and scientific discussions. The distinction also allows for precision in everyday language when exploring the causes or nature of various situations or conditions.

What’s the Plural of Diagnosis?

Singular to Plural Transformation:
The word “diagnosis” follows a pattern typical to words of Greek origin, transforming from -is to -es in its plural form.

Singular Form	Plural Form
diagnosis	diagnoses

Usage Examples:
The correct usage in sentence structure can be illustrated through the following examples:

• A single observation: “The doctor’s diagnosis was confirmed with further tests.”
• Multiple observations: “After reviewing several cases, the different diagnoses pointed towards an environmental cause.”

Grammar Rules:
There are standard rules when pluralizing nouns in English:

• Most nouns simply add an -s or -es.
• Some nouns undergo more significant changes, often due to their Latin or Greek roots.

Possessive Forms Changes:

Singular Possessive	Plural Possessive
diagnosis’s	diagnoses’

• Singular: One diagnosis pertains to a singular assessment.
• Plural: Multiple assessments require the use of diagnoses.

English and Greek Nouns

Regular English nouns typically form their plural by simply adding “-s” or “-es.” For example:

• Cat becomes cats
• Box becomes boxes
• Church becomes churches

However, Greek-origin nouns obey different rules due to their etymology. They often change their endings in the plural form, which might seem irregular to the pattern of English plurals.

Examples of Greek-origin nouns include:

• Basis becomes bases
• Crisis becomes crises
• Thesis becomes theses

The word “diagnosis” is another such noun with a Greek origin.

Singular	Plural
Diagnosis	Diagnoses

• Singular: Diagnosis (pronounced die-ag-nosis)
• Plural: Diagnoses (pronounced die-ag-no-sees)

Examples of “Diagnosis” in Sentences

Singular Usage	Plural Usage
The doctor made a diagnosis based on the patient’s symptoms.	After reviewing multiple patients, the doctor had several diagnoses to consider.
A timely diagnosis can significantly improve the treatment outcome.	The medical conference discussed numerous interesting diagnoses.

Consider these additional examples:

• The specialist provided a diagnosis after the examination.
• In medical journals, one often reads about various new diagnoses.

Common Errors:
Avoid common mistakes such as using “diagnosises” or “diagnosi” which are incorrect forms of the word.

Incorrect	Correct
The lab results arrived, and the doctor has three new diagnosises.	The lab results arrived, and the doctor has three new diagnoses.
John received a second diagnosi for his condition.	John received a second diagnosis for his condition.

Key Takeaways for usage:

• “Diagnosis” is the singular term.
• “Diagnoses” is the plural term.
• Replace “is” with “es” for the plural form.
• Do not use: diagnosises, diagnosies, diagnosi.
• Correct pluralization: diagnoses.

Examples of “Diagnoses” in Sentences

Here are examples that demonstrate the use of “diagnoses” in sentences:

Single vs. Plural:

Singular: Diagnosis	Plural: Diagnoses
The doctor made a diagnosis after reviewing the patient’s symptoms.	The panel of experts reviewed several diagnoses before making a decision.

Contextual Use:

• In medical journals, diagnoses are often listed to compare symptoms and treatments across different cases.
• Multiple diagnoses can complicate a patient’s treatment plan.

Boldly Speaking:

• The clinic specializes in accurate and swift diagnoses of tropical diseases.
• It’s important that she shares her prior diagnoses with the specialist for a comprehensive evaluation.

In Comparison:

• A disease’s diagnosis might be straightforward, whereas multiple diagnoses require extensive investigation.

Synonyms for “Diagnosis”

Here’s a curated list that may aid in diversifying language in a medical or analytical context.

Synonyms Related to Medical Diagnosis:

Synonym	Context of Use
Analysis	Used in discussing the examination of a condition’s nature
Assessment	Refers to the evaluation or estimation of a disease
Determination	Implies a firm decision about an illness
Identification	Denotes the recognition of a disease’s characteristics

Synonyms Related to Analytical Diagnosis:

Synonym	Context of Use
Investigation	Used when examining something methodically
Evaluation	Concerns assessing something’s value or nature
Conclusion	The result or decision reached through analysis
Judgement	Reflects careful consideration to form an opinion or decide

In a clinical context, one might use the term evaluation to discuss the process leading up to a diagnosis, whereas an assessment might refer to both the process and its end product.

• Investigation and analysis are often employed within diagnostic processes that involve detailed examination and systematic inquiry.
• In practice, a conclusion or judgement may reflect the ultimate decision or understanding reached after a thorough diagnostic process.

1. Greek percentage in English
2. Wikipedia: medical diagnosis
3. Diagnosis, Oxford Learner’s Dictionary.
4. Harper, Douglas. “Etymology of diagnosis.” Online Etymology Dictionary, https://www.etymonline.com/word/diagnosis.