Word Roots and Combining Forms

before you start

In this class, you will see many examples of how word parts combine to form words, followed by brief definitions. These definitions emphasize how the meanings of the word parts combine to make the word. For more detailed definitions, remember that you can always refer to the course glossary of terms as a reference.

If you see word parts or words that are bolded, make a note of them because those are the words (glossary terms) you will be expected to know. Don’t forget to continue to keep track of terms for the Unit 3 Touchstone Task assignment. If you have not already done so, download the Excel Template for this assignment to begin tracking them. As you work through the lessons in this course, you will sometimes see clickable tables. You will need information in these tables to answer some Try It questions, so make sure to look at the tables when you work on the questions.

1. Root Words and Combining Forms

You were previously introduced to root words and combining forms. Remember, a root word is the foundation of a medical term that provides its core meaning. A combining form is a root word plus a combining vowel (usually "o"). Combining forms are used to make pronunciation easier. They are used to combine roots with suffixes or other roots.

Remember that all medical terms have at least one word root.

key concept

Word roots commonly specify:

• A body part or organ (such as cardi- for heart, nephr- for kidney).
• A function or action (such as therm- for heat, tox- for poison).
• A disease or condition (such as path- for disease, carcin- for cancer).

1a. Rules

There are general rules for using root words and combing forms in word formation. For example, root words must be combined with suffixes or other roots to form complete terms. Do not use a root word by itself.

There are some other rules that you learned in an earlier lesson. Let’s look at them again with examples.

key concept

1. When connecting a word root and a suffix, a combining vowel is used if the suffix DOES NOT begin with a vowel.

Arthr/o + -itis → Arthritis (inflammation of a joint)

Arthr/o + -plasty → Arthroplasty (surgical repair of a joint)

key concept

2. When connecting a word root and a suffix, a combining vowel is usually NOT USED if the suffix begins with a vowel.

Append + -ectomy → Appendectomy (removal of the appendix; NOT appendeoectomy)

Cardi + -ac → Cardiac (Related to the heart; NOT cardioac)

Path + -ology → Pathology (Study of disease, example of disease, medical specialty; NOT pathoology)

key concept

3. Combining vowels are typically used when joining two root words.

Oste/o + arthr/o + -itis → Osteoarthritis (inflammation of the bones and joints).

Gastr/o + enter/o + -logy → Gastroenterology (study of the digestive tract).

Hyster/o + salping/o + -gram → Hysterosalpingogram (X-ray of the uterus and fallopian tubes).

However, a few exceptions exist. This happens if dropping the second combining vowel improves pronunciation.

1b. Examples Using Rules

Using the rules above, you can construct and break down a wide variety of medical terms that include combining forms.

IN CONTEXT

Here are some examples of complex words that can be broken down into parts.

• Electrocardiogram: Electr/o (electricity) + cardi/o (heart) + -gram (record) → Record of the heart’s electrical activity.
• Neuropathy: Neur/o (nerve) + -pathy (disease) → Nerve disease.
• Gastroesophageal: Gastr/o (stomach) + esophag/o (esophagus) + -eal (pertaining to) → Pertaining to the stomach and esophagus.
• Otolaryngology: Ot/o (ear) + laryng/o (throat) + -logy (study of) → Study of the ears, nose, and throat (ENT).

2. Common Root Words

There are many common root words that are good to know. The expandable table below summarizes examples of some important root words and you will learn many more as you work through this course.

The expandable tables below give examples of root words for body systems and organs; body fluids and substances; conditions, functions, or actions; and directions or positions.

Note that sometimes there is more than one word part with the same or a similar meaning. This is often because the word parts have different origins. In this table, word origins for those terms are specified to illustrate this point.

In this section, we will review examples of root words broken up by categories. The first category is root words for body systems and organs. Some examples are below.

Hepat/o (liver) → Hepatology (study of the liver).

Oste/o (bone) → Osteology (study of bones).

Pulmon/o (lungs) → Pulmonology (study of the lungs).

try it

Let’s try an example. Remember to try to answer the question first, then click on the plus sign to see if you answered correctly.

What term means inflammation of the liver? Use the word parts for “pertaining to the liver” and “inflammation.”

The correct word is hepatitis (hepat/o + -itis).

Next, consider some root words for body fluids and substances. These include essential fluids such as blood, which you are likely to need to reference often. Blood and urine tests (like urinalysis) are very frequently used in medical settings, and you also need to use these terms to refer to medical conditions such as hemophilia (a bleeding disorder) and hematuria (blood in the urine).

Hepat/o (liver) → Hepatology (study of the liver).

Lymph/o (lymph) → Lymphedema (build up of lymph fluid).

try it

Let’s try an example. Use the table above for help.

What term means the study of the urinary system?

The correct word is urology (ur/o + -ology).

The next set of word roots are used often as well. For example, a pathologist is a medical specialist who interprets test results. For example, a pathologist may examine slides from biopsies to determine if cancer cells are present. There are different types of pathologists who specialize in different types of tests. A toxicologist studies the effects of toxins (harmful substances/poisons).

Additional examples are below with short definitions (see the glossary for more detailed definitions).

Path/o (disease) → Pathology (study of the disease).

Tox/o (poison/toxin) → Toxicology (study of poisons/toxins).

try it

Let’s try an example.

What term means a type of cancer that develops in epithelial tissue? Use the word parts for “cancer” and “growth” (or “tumor”).

The correct word is carcinoma (carcin/o + -oma).

The image below shows a carcinoma. This is a type of malignant cancer that develops in epithelial tissue, meaning tissue that covers and protects (like the outer layer of skin). The image shows a specific type of carcinoma in skin. Note the word parts: carcin (cancer) + oma (growth, often a tumor).

This specific example is squamous cell carcinoma, which is one type of carcinoma. Carcinomas develop in epithelial tissue, which is tissue that forms linings. The image below shows epithelial tissue (the outer layer of skin) above deeper skin and muscle. A carcinoma in the outer layer of skin is growing into deeper layers.

You will also regularly use root words for directions and positions. For example, you may need to specify whether a problem is present on one side (unilateral) or on both sides (bilateral). You will learn much more about body positions, directions, and regions in other lessons.

In the illustration below, note that the kidneys are located bilaterally (one on each side).

3. Common Mistakes

As you get used to using medical terms, pay particular attention to common mistakes and terms that can be easily confused. With increasing practice, forming words accurately will feel natural and you will get used to noticing errors intuitively. Try writing medical terms, reading medical documents, and using flashcards and other resources to get as much experience with terms as you can.

Here are some examples of common mistakes associated with using combining forms and root words.

Dropping the combining vowel when it's needed.

Incorrect: Gastrenterology → Correct: Gastroenterology (because “-enterology” starts with a consonant).

Incorrect: Mypathy → Correct: Myopathy (because “pathy” starts with a consonant).

Adding an unnecessary combining vowel.

Incorrect: Nephroitis → Correct: Nephritis (because "-itis" starts with a vowel).

Incorrect: Arthroitis → Correct: Arthritis (because "-itis" starts with a vowel)

Confusing similar-looking root words.

Nephr/o (kidney) vs. Neur/o (nerve).

Arthr/o (joint) vs. Ather/o (fatty plaque).

terms to know

The table below lists terms that are especially important or that may be difficult to pronounce. Audio is provided to help you learn how to say these terms.

REFERENCES

Merriam-Webster. (n.d.). Renal. In Merriam-Webster.com dictionary. Retrieved April 13, 2025, from www.merriam-webster.com/dictionary/renal

Merriam-Webster. (n.d.). -nephros. In Merriam-Webster.com dictionary. Retrieved April 13, 2025, from www.merriam-webster.com/dictionary/-nephros

Merriam-Webster. (n.d.). Derm. In Merriam-Webster.com dictionary. Retrieved April 13, 2025, from www.merriam-webster.com/dictionary/derm

Merriam-Webster. (n.d.). Dermat-. In Merriam-Webster.com dictionary. Retrieved April 13, 2025, from www.merriam-webster.com/dictionary/dermat-

Merriam-Webster. (n.d.). Cutaneo-. In Merriam-Webster.com dictionary. Retrieved April 13, 2025, from www.merriam-webster.com/dictionary/cutaneo-

Merriam-Webster. (n.d.). Hem. In Merriam-Webster.com dictionary. Retrieved April 13, 2025, from www.merriam-webster.com/dictionary/hem

Merriam-Webster. (n.d.). Hemat-. In Merriam-Webster.com dictionary. Retrieved April 13, 2025, from www.merriam-webster.com/dictionary/hemat-