Medical Terminology and Abbreviations

Anatomy, Physiology, Terminology and Disease Recognition · 5 min read

Medical Terminology and Abbreviations

This chapter teaches how medical words are built, gives many common prefixes, roots and suffixes, shows how to break down and build terms, and lists the abbreviations you must know, including The Joint Commission (TJC) "Do Not Use" list.

How Medical Words Are Built

Most medical terms are made from Greek and Latin word parts.

Word root

the core meaning, often a body part. Example: cardi (heart).

Combining vowel

usually "o," added to make the word easy to say. The root plus the vowel is the combining form, written cardi/o.

Prefix

placed before the root to change its meaning, often showing number, position, time or amount. Example: brady- (slow).

Suffix

placed at the end, often showing a condition, procedure or disease. Example: -logy (study of).

To break down a term, start with the suffix, then read the prefix, then the root. Bradycardia breaks into brady- (slow) + cardi (heart) + -ia (condition): a condition of a slow heart. Gastroenterology breaks into gastr/o (stomach) + enter/o (intestine) + -logy (study of): the study of the stomach and intestines.

The combining vowel is dropped before a suffix that begins with a vowel (gastr + -itis = gastritis, not gastroitis) but kept between two roots (gastr/o/enter/itis).

Common Prefixes
Prefix	Meaning	Example
a-, an-	Without, absence of	Apnea (absence of breathing)
brady-	Slow	Bradypnea (slow breathing)
tachy-	Fast	Tachycardia (fast heart rate)
dys-	Painful, difficult	Dysuria (painful urination)
hyper-	Above, excessive	Hypertension (high blood pressure)
hypo-	Below, deficient	Hypoglycemia (low blood sugar)
poly-	Many, much	Polyuria (excessive urination)
peri-	Around	Pericardium (sac around the heart)
endo-	Within	Endoscopy (looking within)
sub-	Under	Subcutaneous (under the skin)
inter- / intra-	Between / within	Intercostal (between ribs); intramuscular (within muscle)

Common Roots and Combining Forms
Combining Form	Meaning	Example
arthr/o	Joint	Arthritis
cardi/o	Heart	Cardiomegaly (enlarged heart)
cyst/o	Bladder, sac	Cystitis
derm/o, dermat/o	Skin	Dermatitis
gastr/o	Stomach	Gastritis
hepat/o	Liver	Hepatitis
nephr/o, ren/o	Kidney	Nephrolithiasis (kidney stones)
neur/o	Nerve	Neuropathy
oste/o	Bone	Osteoporosis
pneum/o, pulmon/o	Lung, air	Pneumonia
hem/o, hemat/o	Blood	Hematuria (blood in urine)
my/o	Muscle	Myalgia (muscle pain)
ot/o	Ear	Otitis media
rhin/o	Nose	Rhinorrhea (runny nose)

Common Suffixes
Suffix	Meaning	Example
-itis	Inflammation	Appendicitis
-ectomy	Surgical removal	Cholecystectomy (gallbladder removal)
-otomy	Cutting into	Tracheotomy
-ostomy	Creating an opening	Colostomy
-algia, -dynia	Pain	Arthralgia
-emia	Blood condition	Anemia, hyperglycemia
-megaly	Enlargement	Hepatomegaly
-scopy	Visual examination	Colonoscopy
-gram / -graph	Record / instrument that records	Electrocardiogram / electrocardiograph
-rrhea	Flow, discharge	Diarrhea
-pnea	Breathing	Dyspnea
-osis	Abnormal condition	Cyanosis
-penia	Deficiency	Thrombocytopenia (low platelets)

Common Trap

-ectomy, -otomy and -ostomy look alike. Removal, cutting into and making an opening are different procedures. A colostomy creates an opening from the colon to the abdominal wall; a colectomy removes part of the colon.

Clinic Scenario

A provider's note reads "patient reports dysphagia." The MA scheduling a swallow study breaks it down: dys- (difficult) + phag (swallow) + -ia means difficulty swallowing. Knowing the word parts lets the MA explain the referral in plain language without adding a diagnosis.

Common Clinical Abbreviations

Common Abbreviations
Abbreviation	Meaning	Abbreviation	Meaning
BP	Blood pressure	NPO	Nothing by mouth
HR	Heart rate	PRN	As needed
RR	Respiratory rate	STAT	Immediately
T	Temperature	b.i.d.	Twice a day
SpO2	Oxygen saturation by pulse oximetry	t.i.d.	Three times a day
Hx	History	q.i.d.	Four times a day
Dx	Diagnosis	q.h.	Every hour (q4h = every 4 hours)
Tx	Treatment	h.s.	At bedtime
Rx	Prescription	a.c. / p.c.	Before meals / after meals
CC	Chief complaint	PO	By mouth
SOB	Shortness of breath	SL	Sublingual (under the tongue)
N/V	Nausea and vomiting	IM / ID	Intramuscular / intradermal
WNL	Within normal limits	subcut / IV	Subcutaneous / intravenous
gtt	Drops

Memory Aid

b.i.d., t.i.d. and q.i.d. count up: bi = 2, tri = 3, quater = 4. The letters "a" and "p" in a.c. and p.c. come from Latin ante (before) and post (after), as in a.m. and p.m.

The Joint Commission Do Not Use List

TJC, the organization that accredits many hospitals and clinics, publishes an official "Do Not Use" list of abbreviations that have caused serious medication errors. The Institute for Safe Medication Practices (ISMP) publishes a longer list of error-prone abbreviations that many offices also follow.

The Joint Commission Do Not Use List
Do Not Use	Why It Is Dangerous	Write Instead
U, u (unit)	Mistaken for 0, 4 or "cc"	unit
IU (international unit)	Mistaken for IV or 10	international unit
Q.D., QD, q.d., qd (daily)	Confused with Q.O.D.; period after Q read as I	daily
Q.O.D., QOD, q.o.d. (every other day)	Confused with Q.D.	every other day
Trailing zero (5.0 mg)	Decimal missed, read as 50 mg	5 mg
Missing leading zero (.5 mg)	Decimal missed, read as 5 mg	0.5 mg
MS, MSO4	Can mean morphine sulfate or magnesium sulfate	morphine sulfate
MgSO4	Confused with MSO4	magnesium sulfate

ISMP also recommends avoiding "cc" (write mL), "SC" or "SQ" (write subcut or subcutaneously) and "hs" (could mean half-strength or bedtime; write "at bedtime").

Exam Tip

The rule for zeros is "always lead, never trail." 0.5 mg is correct; .5 mg and 5.0 mg are both errors. If a question shows an order with a dangerous abbreviation, the best MA action is to ask the provider to clarify or rewrite the order before preparing the drug, not to guess.

Key Takeaways

Break a term into suffix, prefix and root; the combining vowel joins roots and is dropped before a suffix starting with a vowel.
Know the high-frequency parts: -itis, -ectomy, -otomy, -ostomy, -algia, -emia, brady-, tachy-, hyper-, hypo-, dys-.
b.i.d., t.i.d. and q.i.d. mean 2, 3 and 4 times a day; a.c. is before meals, p.c. after meals, PRN as needed, NPO nothing by mouth.
TJC Do Not Use: U, IU, Q.D., Q.O.D., trailing zero, missing leading zero, MS, MSO4, MgSO4.
When an order is unclear or uses an unsafe abbreviation, clarify with the provider before acting.

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Medical Terminology and Abbreviations

How Medical Words Are Built

Most medical terms are made from Greek and Latin word parts.

Word root

the core meaning, often a body part. Example: cardi (heart).

Combining vowel

usually "o," added to make the word easy to say. The root plus the vowel is the combining form, written cardi/o.

Prefix

placed before the root to change its meaning, often showing number, position, time or amount. Example: brady- (slow).

Suffix

placed at the end, often showing a condition, procedure or disease. Example: -logy (study of).

The combining vowel is dropped before a suffix that begins with a vowel (gastr + -itis = gastritis, not gastroitis) but kept between two roots (gastr/o/enter/itis).

Common Prefixes
Prefix	Meaning	Example
a-, an-	Without, absence of	Apnea (absence of breathing)
brady-	Slow	Bradypnea (slow breathing)
tachy-	Fast	Tachycardia (fast heart rate)
dys-	Painful, difficult	Dysuria (painful urination)
hyper-	Above, excessive	Hypertension (high blood pressure)
hypo-	Below, deficient	Hypoglycemia (low blood sugar)
poly-	Many, much	Polyuria (excessive urination)
peri-	Around	Pericardium (sac around the heart)
endo-	Within	Endoscopy (looking within)
sub-	Under	Subcutaneous (under the skin)
inter- / intra-	Between / within	Intercostal (between ribs); intramuscular (within muscle)

Common Roots and Combining Forms
Combining Form	Meaning	Example
arthr/o	Joint	Arthritis
cardi/o	Heart	Cardiomegaly (enlarged heart)
cyst/o	Bladder, sac	Cystitis
derm/o, dermat/o	Skin	Dermatitis
gastr/o	Stomach	Gastritis
hepat/o	Liver	Hepatitis
nephr/o, ren/o	Kidney	Nephrolithiasis (kidney stones)
neur/o	Nerve	Neuropathy
oste/o	Bone	Osteoporosis
pneum/o, pulmon/o	Lung, air	Pneumonia
hem/o, hemat/o	Blood	Hematuria (blood in urine)
my/o	Muscle	Myalgia (muscle pain)
ot/o	Ear	Otitis media
rhin/o	Nose	Rhinorrhea (runny nose)

Common Suffixes
Suffix	Meaning	Example
-itis	Inflammation	Appendicitis
-ectomy	Surgical removal	Cholecystectomy (gallbladder removal)
-otomy	Cutting into	Tracheotomy
-ostomy	Creating an opening	Colostomy
-algia, -dynia	Pain	Arthralgia
-emia	Blood condition	Anemia, hyperglycemia
-megaly	Enlargement	Hepatomegaly
-scopy	Visual examination	Colonoscopy
-gram / -graph	Record / instrument that records	Electrocardiogram / electrocardiograph
-rrhea	Flow, discharge	Diarrhea
-pnea	Breathing	Dyspnea
-osis	Abnormal condition	Cyanosis
-penia	Deficiency	Thrombocytopenia (low platelets)

Common Trap

Clinic Scenario

Common Clinical Abbreviations

Common Abbreviations
Abbreviation	Meaning	Abbreviation	Meaning
BP	Blood pressure	NPO	Nothing by mouth
HR	Heart rate	PRN	As needed
RR	Respiratory rate	STAT	Immediately
T	Temperature	b.i.d.	Twice a day
SpO2	Oxygen saturation by pulse oximetry	t.i.d.	Three times a day
Hx	History	q.i.d.	Four times a day
Dx	Diagnosis	q.h.	Every hour (q4h = every 4 hours)
Tx	Treatment	h.s.	At bedtime
Rx	Prescription	a.c. / p.c.	Before meals / after meals
CC	Chief complaint	PO	By mouth
SOB	Shortness of breath	SL	Sublingual (under the tongue)
N/V	Nausea and vomiting	IM / ID	Intramuscular / intradermal
WNL	Within normal limits	subcut / IV	Subcutaneous / intravenous
gtt	Drops

Memory Aid

b.i.d., t.i.d. and q.i.d. count up: bi = 2, tri = 3, quater = 4. The letters "a" and "p" in a.c. and p.c. come from Latin ante (before) and post (after), as in a.m. and p.m.

The Joint Commission Do Not Use List

The Joint Commission Do Not Use List
Do Not Use	Why It Is Dangerous	Write Instead
U, u (unit)	Mistaken for 0, 4 or "cc"	unit
IU (international unit)	Mistaken for IV or 10	international unit
Q.D., QD, q.d., qd (daily)	Confused with Q.O.D.; period after Q read as I	daily
Q.O.D., QOD, q.o.d. (every other day)	Confused with Q.D.	every other day
Trailing zero (5.0 mg)	Decimal missed, read as 50 mg	5 mg
Missing leading zero (.5 mg)	Decimal missed, read as 5 mg	0.5 mg
MS, MSO4	Can mean morphine sulfate or magnesium sulfate	morphine sulfate
MgSO4	Confused with MSO4	magnesium sulfate

ISMP also recommends avoiding "cc" (write mL), "SC" or "SQ" (write subcut or subcutaneously) and "hs" (could mean half-strength or bedtime; write "at bedtime").

Exam Tip

Key Takeaways

Break a term into suffix, prefix and root; the combining vowel joins roots and is dropped before a suffix starting with a vowel.
Know the high-frequency parts: -itis, -ectomy, -otomy, -ostomy, -algia, -emia, brady-, tachy-, hyper-, hypo-, dys-.
b.i.d., t.i.d. and q.i.d. mean 2, 3 and 4 times a day; a.c. is before meals, p.c. after meals, PRN as needed, NPO nothing by mouth.
TJC Do Not Use: U, IU, Q.D., Q.O.D., trailing zero, missing leading zero, MS, MSO4, MgSO4.
When an order is unclear or uses an unsafe abbreviation, clarify with the provider before acting.

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Answers come only from “Medical Terminology and Abbreviations”. If the chapter doesn't cover it, the coach will say so.

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