Word Building and Word Elements
Elements of a medical term
Every constructed term contains up to four elements: a word root (the core meaning, usually a body part), a combining vowel (nearly always o, occasionally i or e), a prefix (position, number, time, negation, degree), and a suffix (procedure, condition, or grammatical class). A root plus its vowel is a combining form, written with a slash: gastr/o, cardi/o, neur/o.
Four rules that answer most questions
- Keep the combining vowel when the suffix begins with a consonant (gastr/o + -tomy = gastrotomy).
- Drop it when the suffix begins with a vowel (gastr/o + -itis = gastritis).
- Keep it when two roots are joined (gastr/o + enter/o = gastroenter/o).
- Prefixes never take a combining vowel: peri-, not peri/o-.
Traps
Suffixes beginning with -rrh (-rrhagia, -rrhaphy, -rrhea) open with a consonant sound, so the vowel is retained: gastr/o + -rrhagia = gastrorrhagia. Candidates also over-apply the vowel rule and write gastr/o-itis. Finally, not every term has all four elements: cardiac is root plus suffix, and anemia is prefix plus suffix with no root at all.
Worked example
Build "inflammation of the stomach and intestines." Take root gastr + vowel o, then root enter + vowel o. Joining the two roots keeps the first o; the suffix -itis begins with a vowel, so the second o is dropped, giving gastroenteritis. Follow the same two-step check for any built term: locate the suffix first, then decide the vowel.