What elements are added to the root word to change or modify its meaning?
Prefixes, suffixes, and possibly more root words.
Generally, when using more than one word root (as in a compound word) a combining vowel is needed to separate the different word roots regardless of whether the second or third word root begins with a vowel. (There are exceptions to the rule!)
A word cannot end with a combining form (word root + vowel). A suffix is added at the end of the word. A combining vowel will be used if the suffix begins with a consonant. A combining vowel is generally not used if the suffix begins with a vowel (there are some exceptions to this rule).
If the suffix begins with a vowel, the root will attach directly to it. If, however, the suffix begins with a consonant (anything other than a, e, i, o, u, y) the root will need a combining vowel before attaching to the suffix.
The use of more than one word root in a word creates the need for combining vowels to connect the roots. This, in turn, creates combining forms used in compound words. (Applies: words that have several components)
Compound words are usually composed in the following order: combining form + word root + suffix.
The definition of a medical word usually begins with defining the suffix (the word ending) first and continuing to "read" backward through the word as you define it.
When a medical word has a prefix, the definition of the word usually begins with defining the suffix first, the prefix second, and the root(s) last.