Singular & Plural Word Endings in Medical Terminology

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  • 0:02 Medical Terminology
  • 0:36 Basic Rule for Plural Form
  • 1:41 Terms Ending in -Y
  • 2:19 Terms Ending in -IS & -US
  • 3:44 Terms with Other Endings
  • 5:07 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

We are going to look at how medical terms are converted from their singular forms to their plural forms. This lesson will look at the various rules for conversion and give examples.

Medical Terminology

You now know an enormous number of word parts that you can use to create different medical terms. What you need to know now is how to change some of these terms from their singular form to their plural form.

The rules for changing medical terms into the plural form are going to look very familiar to all of those rules that you learned in grade school while learning your first language. And, as always, there are exceptions to the rules. Let's get the general rule out of the way first.

Basic Rule for Plural Form

The easiest way to make a term plural is to simply add the letter 's' to the end. This is one of the most basic rules about pluralization of a term. Luckily for you, this actually works for the vast majority of medical terms. For instance, the term 'endoscope' becomes 'endoscopes.' Since the term ends with a vowel, it is easy to just add 's' at the end to make it plural. That means that this method to make terms plural will work for most terms that end in 'a,' 'e,' 'i,' 'o,' and 'u.'

This rule also works for almost all terms that end in consonants. For example, 'kidney' becomes 'kidneys' and 'immunoglobulin' becomes 'immunoglobulins' when they are put into their plural form using this rule.

Now that we have covered the easy way, let's look at the different sets of exceptions to this rule.

Terms Ending in -Y

The consonant '-y' comes with its own set of rules when it comes to converting terms to the plural form. If the term ends in a vowel followed by the letter 'y,' then you will follow the rule we just discussed and add the letter 's.' In cases when a term ends in a consonant followed by '-y,' you will drop the '-y' and add '-ies' to make the term plural. This is seen in the terms, 'pathology' and 'biopsy,' which become 'pathologies' and 'biopsies' when they are converted.

Terms Ending in -IS and -US

Making a term plural when it ends in 's' can be tricky since there are so many options for making the term plural. When a term already ends in the letter 's,' then some changes have to be made in order to make the term plural. Singular terms that end in 's' usually have either the letter 'I' or 'u' in front of the 's.' For terms that end in '-is,' the 'is' is changed to 'es.' We see this in the term 'diagnosis,' which becomes 'diagnoses' in the plural form.

The rules have included adding 's' in some manner up until now. We always have to have exceptions to the general rules that seem to be way out of left field. Well, here it is! You have to know what to do with those terms that end in '-us.' The '-us' gets dropped, and the letter 'i' is added. Terms that demonstrate this include 'embolus,' which becomes 'emboli,' and 'thrombus,' which becomes 'thrombi.'

There are some exceptions to this rule, too. For some terms ending in '-us,' we simply add '-es' on to the end of the term. We do this when making the plural form for 'fetus.' It becomes 'fetuses.'

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