Spelling and Grammar

Diagnosis vs Diagnoses: Which Word Should You Use?

The words diagnosis (dī-ig-ˈnō-səs) and diagnoses (dī-​ig-​ˈnō-​ˌsēz) look and sound similar. It’s easy to understand why many people are confused about which word to use.

In this article, we’ll provide some clarity around the whole diagnosis vs. diagnoses debate. I’ll provide advice on the correct word to use in a given scenario and we’ll look at examples where the words are used in sentences.

Let’s get started!

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Diagnosis has two primary definitions:

  1. Many people associate the word with established medial practices. Merriam Webster defines diagnosis as the art or act of identifying a disease from its signs and symptoms.
  2. Another widely used definition stipulates that the word can be used in a more general sense. Diagnosis can be used to describe any investigation or analysis of the cause or nature of a condition, situation, or problem.

In both cases, diagnosis is a noun. In the first definition, it is used in a medical context. The second definition could be used to describe the analysis of any condition, situation, or problem.

In very basic terms, a diagnosis is the result of a skilled individual identifying a problem based on tests and observations.

How Do You Use Diagnosis in a Sentence?

Here are a couple of sentences that use the word diagnosis.

Example #1: Paul’s mild symptoms made it very difficult for his doctor to provide a diagnosis.

Example #2: Linda’s mechanic was able to provide a diagnosis quickly when she took her car in for service.

Doctor talking to a patient seated on an examination table.


Diagnoses (dī-​ig-​ˈnō-​ˌsēz) is the plural form of diagnosis.

A doctor might see a single patient and render a diagnosis. The same doctor might examine several patients and provide many diagnoses over the course of a day.

How Do You Use Diagnoses in a Sentence

Here is a sentence containing the word diagnoses.

Example: The hospital administrator asked a new physician to send her a copy of all of his diagnoses for the past week.


What about diagnose? The word diagnose is a verb. It describes the process of identifying the nature of an illness or other problem.

Used in a sentence, you might say “the doctor will diagnose the cause of Bill’s upset stomach after she has examined him”. You could also say “the doctor diagnoses several medical conditions each week”.

Is Everything Clear Now?

Hopefully this article has helped you better understand the subtle differences in meaning behind the whole diagnoses vs diagnosis debate.

It really doesn’t help that the words all sound similar but, as it turns out, each word has a slightly different purpose and meaning.

By Michael Belfry

Working as a full-time training consultant, Michael provides Microsoft Office courses to government and private sector clients across Canada.