Domain 1.2Foundational Knowledge and Medical Terminology
Medical Terminology
Last updated July 11, 2026
Overview
Welcome to your study guide for Medical Terminology! This area of knowledge is the foundation upon which all your clinical and administrative knowledge is built. As a Medical Assistant, you will use this language every single day—when reading physician's orders, documenting in a patient's chart, communicating with other healthcare professionals, and even explaining procedures to patients.
Mastering medical terminology is not about memorizing a dictionary. It's about learning a system. Medical terms are like puzzles; once you understand the pieces (prefixes, roots, and suffixes), you can decode almost any word you encounter. This skill will make you a more efficient, accurate, and confident healthcare professional.
This guide will cover:
- The fundamental building blocks of medical words.
- High-yield prefixes, suffixes, and combining forms (roots).
- Essential abbreviations and the critical "Do Not Use" list.
- Anatomical directions and positions.
- The difference between medical and lay terms.
2. The Building Blocks of Medical Language
Every complex medical term can be broken down into smaller, manageable parts. Understanding these components is the key to unlocking their meaning.
| Word Part | Definition | Function & Example |
|---|---|---|
| Word Root | The core of the word. | Contains the fundamental meaning, usually referring to a body part. Ex: cardi (heart), hepat (liver), gastr (stomach). |
| Prefix | Added to the beginning of a root. | Modifies the root's meaning, often indicating location, time, number, or status. Ex: hyper- (excessive), pre- (before). |
| Suffix | Added to the end of a root. | Further modifies the root's meaning, often indicating a procedure, condition, disease, or disorder. Ex: -itis (inflammation), -ectomy (removal). |
| Combining Vowel | A vowel (usually "o") that links word parts. | Makes the term easier to pronounce. It connects a root to a suffix or a root to another root. Ex: In gastr**o**enterology, the 'o' connects gastr (stomach) and enter (intestine). |
Combining Form: A word root shown with its combining vowel. Example: cardi/o, gastr/o.
Let's break down a term: Gastroenterology
gastr/o= stomach (combining form)enter/o= intestines (combining form)-logy= the study of- Meaning: The study of the stomach and intestines.
⭐ HIGH-YIELD TOPIC: Pluralization Rules
Medical terms often follow Latin or Greek rules for pluralization (making a word plural) rather than just adding an "s".
| Ending Rule | Singular Example | Plural Example | Memory Aid |
|---|---|---|---|
| -a ➔ -ae | Vertebra | Vertebrae | Think of "algae" or "larvae". |
| -us ➔ -i | Bronchus | Bronchi | Fungus ➔ Fungi. |
| -um ➔ -a | Bacterium | Bacteria | Datum ➔ Data. |
| -is ➔ -es | Diagnosis | Diagnoses | Crisis ➔ Crises. |
| -ex/-ix ➔ -ices | Apex, Appendix | Apices, Appendices | Index ➔ Indices. |
3. High-Yield Prefixes: The Modifiers
Prefixes are placed at the beginning of a word to change its meaning. Pay close attention to pairs of opposites (e.g., hyper-/hypo-, tachy-/brady-).
| Prefix | Meaning | Example Term | Memory Aid |
|---|---|---|---|
| hyper- | Excessive, above, beyond | Hypertension (high blood pressure) | A hyperactive person has excessive energy. |
| hypo- | Below, under, deficient | Hypoglycemia (low blood sugar) | A hypodermic needle goes under the skin. |
| tachy- | Fast, rapid | Tachycardia (fast heart rate) | A car's tachometer measures engine speed. |
| brady- | Slow | Bradycardia (slow heart rate) | Brady the sloth is famously very slow. |
| dys- | Bad, difficult, painful | Dysphagia (difficulty swallowing) | A dysfunctional system is bad or difficult to use. |
| a-, an- | Without, not | Afebrile (without fever) | Asymptomatic means without symptoms. |
| endo- | Within, inner | Endoscope (instrument to look inside) | An endoscope is used to see inside the body. |
| peri- | Around, surrounding | Pericardium (sac surrounding the heart) | The perimeter is the measurement around a shape. |
| ab- | Away from | Abduction (moving a limb away from the body) | To be abducted is to be taken away. |
| ad- | Toward, to add to | Adduction (moving a limb toward the body) | To add a limb back to the body. |
| anti- | Against | Antibiotic (works against bacteria) | An antidote works against poison. |
| inter- | Between | Intercostal (between the ribs) | An intermission is a break between acts of a play. |
| sub- | Under, below | Subcutaneous (under the skin) | A submarine travels under the water. |
4. High-Yield Suffixes: The Describers
Suffixes come at the end of a word and usually describe a condition, disease process, or procedure.
Suffixes Related to Procedures
| Suffix | Meaning | Example Term | Memory Aid |
|---|---|---|---|
| -ectomy | Excision, surgical removal | Hysterectomy (removal of the uterus) | 'E' for Excise or Exit. The part is removed. |
| -tomy | Incision, to cut into | Phlebotomy (incision into a vein) | To study anatomy, you often have to make a cut. |
| -stomy | Surgical creation of an opening | Colostomy (creating an opening for the colon) | A stoma is an opening. |
| -plasty | Surgical repair, molding | Rhinoplasty (surgical repair of the nose) | Think of plastic surgery—molding or repairing. |
| -graphy | Process of recording | Electrocardiography (process of recording the heart's electrical activity) | The process of taking a photograph. |
| -gram | The record or image | Electrocardiogram (the EKG tracing itself) | A telegram is a record of a message. |
Suffixes Related to Conditions & Diseases
| Suffix | Meaning | Example Term | Memory Aid |
|---|---|---|---|
| -itis | Inflammation | Tonsillitis (inflammation of the tonsils) | A mosquito bites you, causing inflammation. |
| -oma | Tumor, mass | Lipoma (fatty tumor) | Carcinoma is a cancerous tumor. |
| -pathy | Disease | Encephalopathy (disease of the brain) | Pathology is the study of disease. |
| -megaly | Enlargement | Hepatomegaly (enlargement of the liver) | Mega means very large. |
| -penia | Deficiency, lack of | Leukopenia (deficiency of white blood cells) | You need a pen to write; a deficiency means you lack one. |
| -stenosis | Abnormal narrowing | Carotid stenosis (narrowing of the carotid artery) | A stent is used to open a narrowed vessel. |
| -sclerosis | Abnormal hardening | Arteriosclerosis (hardening of the arteries) | Think of a scar—it's hard tissue. |
| -malacia | Abnormal softening | Osteomalacia (softening of the bones) | Sounds like malleable, which means soft. |
| -lysis | Destruction, breakdown | Hemolysis (destruction of red blood cells) | Lysol spray destroys germs. |
| -rrhea | Discharge, flow | Diarrhea (excessive flow of stool) | The common word diarrhea is your best clue. |
| -algia/-dynia | Pain | Myalgia (muscle pain), Gastrodynia (stomach pain) | Dynamite causes explosive pain. |
Suffixes Related to Bodily Functions
| Suffix | Meaning | Example Term | Memory Aid |
|---|---|---|---|
| -pnea | Breathing | Apnea (without breath) | Pneumonia is a lung infection affecting breathing. |
| -phagia | Swallowing, eating | Dysphagia (difficulty swallowing) | The pharynx/esophagus is your gullet for swallowing. |
| -phasia | Speaking | Aphasia (inability to speak) | You use a phrase when speaking. |
5. High-Yield Combining Forms (Word Roots)
These are the core foundations of medical terms, often referring to a body part, organ, or color.
| Combining Form | Meaning | Example Term |
|---|---|---|
| cardi/o | Heart | Cardiology (study of the heart) |
| hepat/o | Liver | Hepatitis (inflammation of the liver) |
| nephr/o, ren/o | Kidney | Nephrology, Renal failure |
| gastr/o | Stomach | Gastritis (inflammation of the stomach) |
| oste/o | Bone | Osteoporosis (porous bone condition) |
| arthr/o | Joint | Arthritis (inflammation of a joint) |
| encephal/o | Brain | Encephalopathy (disease of the brain) |
| esthesi/o | Sensation, feeling | Paresthesia (abnormal sensation like pins and needles) |
| hist/o | Tissue | Histology (study of tissues) |
| onych/o | Nail | Onychomycosis (fungal infection of the nail) |
| salping/o | Fallopian tube | Salpingectomy (removal of a fallopian tube) |
| choledoch/o | Common bile duct | Choledochojejunostomy (anastomosis of bile duct & jejunum) |
| erythr/o | Red | Erythrocyte (red blood cell) |
| leuk/o | White | Leukocyte (white blood cell) |
| melan/o | Black, dark | Melanoma (dark-pigmented skin cancer) |
| cyan/o | Blue | Cyanosis (bluish skin discoloration) |
6. Common Abbreviations, Acronyms, and Symbols
Abbreviations are medical shorthand. Accuracy is critical, as a misplaced decimal or misread letter can cause serious patient harm.
Medication and Prescription Abbreviations
| Abbreviation | Latin Origin | Meaning |
|---|---|---|
| p.o. | Per Os | By mouth |
| NPO | Nil Per Os | Nothing by mouth |
| b.i.d. | Bis in Die | Twice a day |
| t.i.d. | Ter in Die | Three times a day |
| q.i.d. | Quater in Die | Four times a day |
| q | Quaque | Every (e.g., q2h = every 2 hours) |
| ac | Ante Cibum | Before meals |
| pc | Post Cibum | After meals |
| h.s. | Hora Somni | At bedtime (hour of sleep) |
| prn | Pro Re Nata | As needed |
| stat | Statim | Immediately |
| D/c | Discontinue / Discharge | |
| SL | Sublingual (under the tongue) | |
| PR | Per Rectum | |
| SC | Subcutaneous | |
| IM | Intramuscular |
Clinical and Administrative Abbreviations
| Abbreviation | Meaning | Mnemonic / Note |
|---|---|---|
| CPR | Cardiopulmonary Resuscitation | Emergency procedure. |
| HTN | Hypertension | High blood pressure (Hyper-TensioN). |
| OR | Operating Room | Where surgery happens. |
| CPE | Complete Physical Examination | Head-to-toe checkup. |
| CBC | Complete Blood Count | Common blood test. |
The Joint Commission (TJC) "Do Not Use" List
This is a CRITICAL safety topic for the medical assistant exam and your career. The Joint Commission has identified a list of abbreviations that are prone to error and must be avoided in clinical documentation.
- Do Not Use:
U, u(for unit) → Why? Can be mistaken for "0", "4", or "cc". Instead, write: "unit".- Do Not Use:
IU(for International Unit) → Why? Can be mistaken for "IV" (intravenous) or the number "10". Instead, write: "International Unit".- Do Not Use:
Q.D., QD, q.d., qd(for daily) → Why? Can be mistaken for "QID" (four times a day). Instead, write: "daily" or "every day".- Do Not Use:
Q.O.D., QOD, q.o.d., qod(for every other day) → Why? Can be mistaken for "QD" or "QID". Instead, write: "every other day".- Do Not Use: Trailing zero (e.g.,
X.0 mg) and Lack of a leading zero (e.g.,.X mg) → Why? A decimal point can be missed. Instead, write:X mgand0.X mg.
7. Positional and Directional Terminology
These terms describe the location of a structure in relation to other structures, based on the body being in the anatomical position (standing upright, facing forward, arms at the side, palms forward).
| Term Pair | Meaning | Example |
|---|---|---|
| Anterior (Ventral) / Posterior (Dorsal) | Front / Back | The sternum is anterior to the spine. A dolphin's dorsal fin is on its back. |
| Superior / Inferior | Above / Below | The head is superior to the neck. The foot is inferior to the knee. |
| Medial / Lateral | Toward midline / Away from midline | The nose is medial to the eyes. The ears are lateral to the nose. |
| Proximal / Distal | Closer to point of attachment / Farther from point of attachment | The elbow is proximal to the wrist. The fingers are distal to the wrist. Think distal = distant. |
| Superficial / Deep | Closer to the surface / Farther from the surface | The skin is superficial to the muscles. The bones are deep to the skin. |
8. Lay Terms vs. Medical Terms
As an MA, you must be "bilingual"—able to speak the precise language of medicine with colleagues and use clear, common terms with patients.
| Medical Term | Common (Lay) Term |
|---|---|
| Malaise | A general feeling of discomfort or illness |
| Pyrexia | Fever |
| Prognosis | A forecast of a disease's likely outcome |
| Larynx | Voice box |
| Micturition | Urination, voiding |
| Epistaxis | Nosebleed |
| Hypertension | High Blood Pressure |
| Myocardial Infarction | Heart Attack |
9. Final Key Takeaways
- Break It Down: When you see a long, intimidating word, don't panic. Look for the prefix, suffix, and root. Decode each piece to find the meaning.
- Opposites Attract Questions: Know the difference between opposing pairs like hyper/hypo, tachy/brady, ab/ad, and anterior/posterior. These are common exam questions.
- Safety First: Memorize The Joint Commission's "Do Not Use" list. Questions about
QDand trailing zeros are very likely because they are major patient safety issues. - Context is Key:
C.C.means Chief Complaint in a patient history but can mean "cubic centimeter" in a lab context (though "mL" is preferred). Pay attention to the scenario in the question. - Know Your Routes: Be able to instantly recognize
p.o.,SL,PR,IM, andSCas they are fundamental to medication administration. - -phagia vs. -phasia: Don't mix them up! -phagia (with a 'g') is for your gullet (swallowing). -phasia (with an 's') is for speech.
- Practice with Flashcards: The best way to learn this volume of information is through active recall. Make flashcards for prefixes, suffixes, roots, and abbreviations. You will see them repeatedly on the medical assistant certification exam.