The stem (as it will be referred to from now on) is the main component of a medical term. It usually indicates the organ or body part being described. All words have a stem and often two stem words are combined to describe with even more specificity.
When two stems are combined it is often necessary to insert a vowel between them to aid in pronunciation. This is especially true when the first word ends in a consonant and the second word also begins in a consonant. For example:
Thermometer = therm+ o +meter
While other vowels may be used occasionally, "o" is the most common. The next several pages will outline the major body systems and the stems associated with each.