Key Takeaways
- Medical terms are built from three components: prefix (beginning), root (core meaning), and suffix (ending)
- Common prefixes: hyper- (excessive), hypo- (under/below), tachy- (fast), brady- (slow), poly- (many), a-/an- (without)
- Common roots: cardi/o (heart), pulmon/o (lung), neur/o (nerve), hepat/o (liver), ren/o (kidney), dermat/o (skin)
- Common suffixes: -itis (inflammation), -ectomy (surgical removal), -ology (study of), -emia (blood condition), -osis (condition/disease)
- Breaking unfamiliar medical terms into prefix + root + suffix helps decode their meaning
- Combining vowels (usually "o") connect word roots to suffixes or other roots when the suffix begins with a consonant
- The HESI A2 tests both medical vocabulary and general English vocabulary in context
- Directional terms: anterior (front), posterior (back), superior (above), inferior (below), medial (toward center), lateral (toward side)
Last updated: February 2026
Medical Terminology & Word Roots
Medical terminology may seem intimidating, but most medical terms are built from a set of common word parts. Learning these parts gives you the ability to decode thousands of terms you have never seen before.
Building Medical Terms
Every medical term is constructed from one or more of these components:
| Component | Position | Function | Example |
|---|---|---|---|
| Prefix | Beginning | Modifies or qualifies the root | hyper- (excessive), sub- (under) |
| Root | Middle (core) | Core meaning of the term | cardi (heart), derm (skin) |
| Suffix | End | Indicates procedure, condition, or specialization | -itis (inflammation), -ectomy (removal) |
| Combining vowel | Between parts | Connects parts for pronunciation (usually "o") | cardi-o-logy, gastr-o-scope |
Example Breakdown:
- Tachycardia = tachy (fast) + cardi (heart) + -ia (condition) = "condition of fast heart rate"
- Hepatomegaly = hepat/o (liver) + -megaly (enlargement) = "enlargement of the liver"
- Subcutaneous = sub- (under) + cutane (skin) + -ous (pertaining to) = "pertaining to under the skin"
Essential Prefixes
| Prefix | Meaning | Example |
|---|---|---|
| a- / an- | Without, absence of | Apnea (without breathing) |
| anti- | Against | Antibiotic (against life/bacteria) |
| bi- | Two | Bilateral (two sides) |
| brady- | Slow | Bradycardia (slow heart rate) |
| dys- | Difficult, painful, abnormal | Dyspnea (difficult breathing) |
| endo- | Within | Endoscopy (looking within) |
| epi- | Upon, above | Epidermis (upon the skin) |
| hemi- | Half | Hemiplegia (paralysis of half the body) |
| hyper- | Excessive, above normal | Hypertension (high blood pressure) |
| hypo- | Under, below normal | Hypoglycemia (low blood sugar) |
| inter- | Between | Intercostal (between the ribs) |
| intra- | Within | Intravenous (within the vein) |
| peri- | Around | Pericardium (around the heart) |
| poly- | Many, excessive | Polyuria (excessive urination) |
| post- | After | Postoperative (after surgery) |
| pre- | Before | Prenatal (before birth) |
| sub- | Under, below | Sublingual (under the tongue) |
| tachy- | Fast | Tachypnea (fast breathing) |
Essential Roots
| Root | Meaning | Example |
|---|---|---|
| cardi/o | Heart | Cardiology (study of the heart) |
| cephal/o | Head | Cephalic (pertaining to the head) |
| cyt/o | Cell | Cytology (study of cells) |
| derm/o, dermat/o | Skin | Dermatitis (inflammation of skin) |
| gastr/o | Stomach | Gastritis (inflammation of stomach) |
| hem/o, hemat/o | Blood | Hematoma (collection of blood) |
| hepat/o | Liver | Hepatitis (inflammation of liver) |
| my/o | Muscle | Myalgia (muscle pain) |
| nephr/o, ren/o | Kidney | Nephritis (inflammation of kidney) |
| neur/o | Nerve | Neurology (study of nerves) |
| oste/o | Bone | Osteoporosis (porous bones) |
| pneum/o, pulmon/o | Lung | Pneumonia (lung infection) |
| vas/o | Vessel | Vascular (pertaining to vessels) |
Essential Suffixes
| Suffix | Meaning | Example |
|---|---|---|
| -algia | Pain | Myalgia (muscle pain) |
| -ectomy | Surgical removal | Appendectomy (removal of appendix) |
| -emia | Blood condition | Anemia (without adequate blood) |
| -itis | Inflammation | Arthritis (inflammation of joints) |
| -logy / -ology | Study of | Pathology (study of disease) |
| -megaly | Enlargement | Cardiomegaly (enlarged heart) |
| -oma | Tumor, mass | Melanoma (tumor of melanocytes) |
| -osis | Condition, disease | Cyanosis (condition of blueness) |
| -pathy | Disease | Neuropathy (disease of nerves) |
| -plasty | Surgical repair | Rhinoplasty (surgical repair of nose) |
| -scope | Instrument for viewing | Stethoscope (instrument for chest sounds) |
| -scopy | Visual examination | Endoscopy (viewing inside) |
| -tomy / -otomy | Incision, cutting into | Tracheotomy (incision into trachea) |
Combining Forms: More Examples
Understanding how parts combine helps decode complex terms:
| Term | Prefix | Root | Suffix | Meaning |
|---|---|---|---|---|
| Hyperglycemia | hyper- (excessive) | glyc (sugar) | -emia (blood condition) | Excessive sugar in blood |
| Polyuria | poly- (many) | ur (urine) | -ia (condition) | Excessive urination |
| Dyspnea | dys- (difficult) | pne (breathing) | -a (condition) | Difficulty breathing |
| Subcutaneous | sub- (under) | cutane (skin) | -ous (pertaining to) | Under the skin |
| Pericarditis | peri- (around) | card (heart) | -itis (inflammation) | Inflammation around the heart |
| Endoscopy | endo- (within) | scop (look/examine) | -y (process) | Process of looking within |
| Cholecystectomy | — | cholecyst (gallbladder) | -ectomy (removal) | Removal of the gallbladder |
| Apnea | a- (without) | pne (breathing) | -a (condition) | Without breathing |
| Intravenous | intra- (within) | ven (vein) | -ous (pertaining to) | Within the vein |
| Postoperative | post- (after) | operat (surgery) | -ive (pertaining to) | After surgery |
Common Abbreviations in Healthcare
While not traditional medical terminology, the HESI A2 may test common healthcare abbreviations:
| Abbreviation | Meaning | Abbreviation | Meaning |
|---|---|---|---|
| BP | Blood pressure | Rx | Prescription |
| HR | Heart rate | Tx | Treatment |
| RR | Respiratory rate | Dx | Diagnosis |
| Temp | Temperature | Hx | History |
| VS | Vital signs | Sx | Symptoms |
| BID | Twice a day | PRN | As needed |
| TID | Three times a day | STAT | Immediately |
| QID | Four times a day | NPO | Nothing by mouth |
Additional Medical Abbreviations Commonly Tested
| Abbreviation | Meaning | Context |
|---|---|---|
| ADL | Activities of daily living | Patient function assessment |
| I&O | Intake and output | Fluid monitoring |
| WNL | Within normal limits | Lab results / assessments |
| SOB | Shortness of breath | Respiratory assessment |
| UTI | Urinary tract infection | Common diagnosis |
| CHF | Congestive heart failure | Cardiac diagnosis |
| DVT | Deep vein thrombosis | Vascular diagnosis |
| ROM | Range of motion | Physical assessment |
| OTC | Over the counter | Medication classification |
| IV | Intravenous | Route of administration |
| IM | Intramuscular | Route of administration |
| PO | By mouth (per os) | Route of administration |
| SQ/SubQ | Subcutaneous | Route of administration |
"Do Not Use" abbreviations (The Joint Commission):
- U for units — write "units" instead (can be mistaken for 0 or 4)
- QD for daily — write "daily" instead (can be mistaken for QID)
- MS — write "morphine sulfate" or "magnesium sulfate" (can be confused)
- Trailing zeros (5.0 mg) — write "5 mg" instead (decimal can be missed)
- Lack of leading zero (.5 mg) — write "0.5 mg" instead
Word Building Practice
Building terms systematically:
Root: GASTR/O (stomach)
- Gastritis = stomach inflammation
- Gastroscopy = visual examination of the stomach
- Gastrectomy = surgical removal of the stomach
- Gastroenteritis = inflammation of the stomach and intestines
Root: CARDI/O (heart)
- Cardiology = study of the heart
- Cardiomegaly = enlargement of the heart
- Carditis = inflammation of the heart
- Tachycardia = fast heart rate
- Bradycardia = slow heart rate
- Electrocardiogram (ECG/EKG) = recording of the heart's electrical activity
Root: NEUR/O (nerve)
- Neurology = study of the nervous system
- Neuropathy = disease of the nerves
- Neuritis = inflammation of a nerve
- Neuroma = tumor of nerve tissue
- Neuralgia = nerve pain
Root: PULMON/O (lung)
- Pulmonology = study of the lungs
- Pulmonary = pertaining to the lungs
- Pulmonectomy = surgical removal of a lung
Root: OSTE/O (bone)
- Osteoporosis = porous bones (loss of bone density)
- Osteotomy = incision into bone
- Osteomyelitis = bone infection (inflammation of bone marrow)
- Osteoarthritis = joint disease involving bone
Body Position and Direction Terms in Medical Orders
Medical orders frequently use positional terminology:
| Term | Meaning | Context |
|---|---|---|
| PO | Per os (by mouth) | Oral medication administration |
| IV | Intravenous | Medication given through a vein |
| IM | Intramuscular | Injection into a muscle |
| SQ / SC | Subcutaneous | Injection under the skin |
| ID | Intradermal | Injection into the skin (TB test) |
| PR | Per rectum | Rectal medication administration |
| SL | Sublingual | Under the tongue |
| Topical | Applied to skin surface | Creams, ointments, patches |
Commonly Tested Vocabulary — Additional Words
| Word | Definition | Example Sentence |
|---|---|---|
| Abstain | To refrain from | "The patient was advised to abstain from alcohol." |
| Acute | Sharp, severe; sudden onset | "The patient presented with acute abdominal pain." |
| Audible | Able to be heard | "Breath sounds were audible on auscultation." |
| Compensate | To make up for | "The heart compensates for low volume by increasing rate." |
| Contingent | Dependent on | "Discharge is contingent upon stable vital signs." |
| Depress | To press down; to lower | "Depress the plunger slowly when injecting." |
| Dilate | To widen or expand | "The pupils dilate in response to darkness." |
| Elicit | To draw out or provoke | "Elicit a pain response by applying pressure." |
| Fluctuate | To change irregularly | "Blood sugar levels may fluctuate throughout the day." |
| Incidence | Rate of occurrence | "The incidence of diabetes has increased in recent years." |
| Latent | Present but not visible or active | "The virus remained latent for years before reactivation." |
| Ominous | Threatening, foreshadowing something bad | "The ominous lab results prompted immediate intervention." |
| Parameter | A measurable factor | "Monitor the patient's hemodynamic parameters." |
| Precaution | A measure taken to prevent harm | "Standard precautions include hand hygiene and PPE." |
| Resilient | Able to recover quickly | "Children are often more resilient than adults after surgery." |
| Subtle | Not immediately obvious | "The subtle changes in mental status were noted." |
| Symptomatic | Showing symptoms | "The patient became symptomatic after exposure." |
| Therapeutic | Having healing properties | "The therapeutic dose was effective in reducing symptoms." |
| Transient | Temporary, lasting a short time | "The patient experienced transient dizziness upon standing." |
| Unilateral | Affecting one side | "The patient reported unilateral leg weakness." |
| Vital | Essential to life | "Monitoring vital signs is a core nursing skill." |
| Potent | Strong, powerful | "The medication was potent and required careful dosing." |
| Palpable | Can be felt by touch | "The mass was palpable during the abdominal exam." |
| Proximal | Nearest to the point of attachment | "The fracture was at the proximal end of the femur." |
| Bilateral | Affecting both sides | "Bilateral crackles were heard on lung auscultation." |
| Occlude | To block or close off | "The clot may occlude the coronary artery." |
| Distend | To swell or expand | "The abdomen was visibly distended." |
| Aseptic | Free from contamination | "Maintain aseptic technique during catheter insertion." |
| Benign | Not harmful; not cancerous | "The biopsy confirmed the tumor was benign." |
| Malignant | Harmful, cancerous, tending to spread | "The malignant cells had metastasized to the lymph nodes." |
Homonyms, Homophones, and Homographs
Understanding these word relationships is important for the HESI A2:
| Type | Definition | Examples |
|---|---|---|
| Homophones | Sound alike, different spelling/meaning | their/there/they're, to/too/two, sight/site/cite |
| Homographs | Spelled alike, different pronunciation/meaning | lead (to guide) / lead (metal), wound (injury) / wound (past tense of wind) |
| Homonyms | Same spelling AND pronunciation, different meaning | bark (tree covering) / bark (dog sound), bank (financial) / bank (river edge) |
Common homophones tested on the HESI A2:
| Words | Meanings |
|---|---|
| affect / effect | Affect = verb (influence); Effect = noun (result) |
| stationary / stationery | Stationary = not moving; Stationery = writing materials |
| complement / compliment | Complement = complete; Compliment = praise |
| principal / principle | Principal = main/leader; Principle = rule/belief |
| discrete / discreet | Discrete = separate; Discreet = careful/private |
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Test Your Knowledge
What does the term "tachycardia" mean?
A
B
C
D
Test Your Knowledge
The suffix "-ectomy" means:
A
B
C
D
Test Your KnowledgeFill in the Blank
The prefix "hypo-" means _____ or below normal.
Type your answer below
Test Your Knowledge
Which term means "inflammation of the liver"?
A
B
C
D
Test Your KnowledgeMatching
Match each medical prefix to its correct meaning.
Match each item on the left with the correct item on the right
1
brady-
2
tachy-
3
hyper-
4
poly-
5
a- / an-
Test Your Knowledge
Break down the term "endoscopy" into its components. What does it mean?
A
B
C
D