How to medical spellings
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rules for spelling medical terms prefixes suffixes roots guide
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Here is a practical guide to spelling medical terms correctly. Most medical words are built from Greek and Latin word parts, and once you know the rules, you can spell (and decode) almost any term.
How Medical Spelling Works
Medical terms are constructed from three building blocks:
| Part | Position | Function |
|---|---|---|
| Root (word root) | Core of the word | Identifies the body part or concept |
| Prefix | Before the root | Modifies meaning (location, number, time, status) |
| Suffix | After the root | Describes a condition, procedure, or process |
| Combining vowel | Between roots | Usually "o" -- connects root to suffix when the suffix starts with a consonant |
Rule 1: The Combining Vowel "o"
The most common source of spelling errors. The combining vowel (usually o) links a root to a suffix that starts with a consonant.
- cardi (heart) + o + logy = cardiology
- gastr (stomach) + o + scope = gastroscope
- arthr (joint) + o + plasty = arthroplasty
Drop the "o" when the suffix begins with a vowel:
- gastr + itis = gastritis (not gastroitis)
- arthr + itis = arthritis (not arthroitis)
Rule 2: Common Prefixes to Know
| Prefix | Meaning | Example |
|---|---|---|
| a- / an- | without, not | anemia, apnea |
| brady- | slow | bradycardia |
| tachy- | fast | tachycardia |
| hyper- | above normal, excessive | hypertension |
| hypo- | below normal, deficient | hypoglycemia |
| inter- | between | intercostal |
| intra- | within | intravenous |
| poly- | many | polyuria |
| peri- | around | pericardium |
| sub- | under, below | subcutaneous |
| supra- | above | suprarenal |
| bi- | two | bilateral |
| uni- | one | unilateral |
| dys- | painful, difficult, abnormal | dyspnea, dysphagia |
| neo- | new | neoplasm |
Rule 3: Common Suffixes to Know
| Suffix | Meaning | Example |
|---|---|---|
| -itis | inflammation | appendicitis |
| -ectomy | surgical removal | appendectomy |
| -ostomy | surgical opening | colostomy |
| -otomy | incision into | tracheotomy |
| -plasty | surgical repair | rhinoplasty |
| -scopy | visual examination | colonoscopy |
| -logy | study of | pathology |
| -ology | study of | cardiology |
| -algia | pain | neuralgia |
| -emia | blood condition | anemia, leukemia |
| -oma | tumor | carcinoma |
| -pathy | disease | neuropathy |
| -rrhea | flow, discharge | diarrhea |
| -rrhage | bursting forth / hemorrhage | hemorrhage |
| -stenosis | narrowing | aortic stenosis |
| -megaly | enlargement | hepatomegaly |
| -gram | record / image | electrocardiogram |
| -graph | instrument for recording | electrocardiograph |
Rule 4: Common Roots by Body System
| Root | Meaning | Example |
|---|---|---|
| cardi/o | heart | cardiology |
| hepat/o | liver | hepatitis |
| nephr/o | kidney | nephrology |
| neur/o | nerve | neurology |
| oste/o | bone | osteoporosis |
| dermat/o | skin | dermatitis |
| pulmon/o | lung | pulmonary |
| gastr/o | stomach | gastritis |
| hem/o, hemat/o | blood | hematology |
| arthr/o | joint | arthritis |
| my/o | muscle | myopathy |
| encephal/o | brain | encephalitis |
| rhin/o | nose | rhinoplasty |
| ophthalm/o | eye | ophthalmology |
| ot/o | ear | otoscope |
Rule 5: Silent and Tricky Letter Patterns
Several Greek-origin terms have unusual letter combinations that trip up spellers:
- "pn" at the start: pneumonia, pneumothorax (the "p" is silent)
- "ps" at the start: psychology, psoriasis (the "p" is silent)
- "ph" = "f" sound: pharynx, phlebitis, dysphagia
- "rh" or "rrh": rhinitis, diarrhea, hemorrhage (double "r" in the middle of a word)
- "y" as a vowel: tympanic, myocardium, lymph
- "ae" or "oe": older spellings like oedema (British) vs edema (American); gynaecology vs gynecology
Rule 6: Plural Forms
Medical plurals follow Latin/Greek rules, not standard English "-s":
| Singular ending | Plural ending | Example |
|---|---|---|
| -a | -ae | vertebra → vertebrae |
| -um | -a | bacterium → bacteria |
| -us | -i | bronchus → bronchi |
| -is | -es | diagnosis → diagnoses |
| -ix / -ex | -ices | appendix → appendices |
| -on | -a | ganglion → ganglia |
Practical Tips
- Break the word down - identify prefix + root + suffix before spelling
- Learn the 10 most common roots first (cardi, hepat, nephr, neur, gastr, hem, pulmon, arthr, dermat, oste)
- Remember the "o" rule - use it before consonants, drop it before vowels
- British vs American spelling - be consistent (e.g., oedema vs edema, haemoglobin vs hemoglobin)
- Double letters in compound words are common (e.g., intraabdominal can become intra-abdominal)
Once you internalize these patterns, you can reliably spell and decode terms you have never seen before. For example, hepatosplenomegaly = hepat/o (liver) + splen/o (spleen) + megaly (enlargement) = enlargement of both the liver and spleen.
How to learn ecg
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how to learn ECG reading interpretation step by step beginner guide
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Here is a structured guide to learning ECG interpretation, built around the systematic approach described in Harrison's Principles of Internal Medicine (22nd Edition).
How to Learn ECG Interpretation
Step 1 - Understand What an ECG Records
An ECG (electrocardiogram) records the electrical activity of the heart from 12 different "camera angles" (leads). Each lead sees the same heart events from a different spatial direction.
The 12 leads split into:
- 6 limb leads (I, II, III, aVR, aVL, aVF) - look at the heart in the frontal plane
- 6 precordial leads (V1-V6) - look at the heart in the horizontal plane
Step 2 - Learn the Waveforms First
Every heartbeat produces a repeating pattern of waves. Memorize what each wave represents before anything else:
| Wave/Segment | What it Represents |
|---|---|
| P wave | Atrial depolarization (atria contracting) |
| PR interval | Time from atrial to ventricular activation (includes AV node delay) |
| QRS complex | Ventricular depolarization (ventricles contracting) |
| ST segment | Early ventricular repolarization (key area for ischemia) |
| T wave | Ventricular repolarization |
| U wave | Sometimes seen; may relate to repolarization of Purkinje fibers |
| QT interval | Total ventricular depolarization + repolarization time |
Step 3 - Learn the Normal Values
Commit these numbers to memory early:
| Measurement | Normal Range |
|---|---|
| Heart rate | 60-100 bpm |
| PR interval | 120-200 ms (3-5 small squares) |
| QRS duration | < 100-110 ms (< 2.5 small squares) |
| QTc | < 450 ms (men), < 460 ms (women) |
| P wave duration | 60-120 ms |
Grid reminder: Each small square = 40 ms (horizontal), 0.1 mV (vertical). Each large square = 200 ms / 0.5 mV.
Step 4 - Use a Systematic 14-Step Approach Every Time
According to Harrison's, every ECG must be assessed for these 14 parameters in order - never skip steps:
- Standardization/calibration - Is the paper speed 25 mm/s? Is gain set to 1 mV = 10 mm?
- Rhythm - Sinus or not? Regular or irregular?
- Heart rate - Count R-R intervals (300 ÷ large squares between R waves)
- PR interval - Normal, short (pre-excitation), or prolonged (AV block)?
- QRS duration - Narrow or wide? Wide = bundle branch block or ventricular origin
- QT/QTc interval - Prolonged = arrhythmia risk
- Mean QRS electrical axis - Normal, left axis deviation, or right axis deviation?
- P waves - Present? Morphology normal? One before each QRS?
- QRS voltages - Low voltage or high voltage (LVH/RVH)?
- Precordial R-wave progression - R wave should grow from V1 to V5/V6
- Abnormal Q waves - Pathological Q waves = old infarction
- ST segments - Elevated or depressed? Pattern of leads affected?
- T waves - Inverted, peaked, or flat?
- U waves - Prominent U waves (hypokalemia, bradycardia)?
"Many mistakes in ECG interpretation are errors of omission. Therefore, a systematic approach is essential." - Harrison's Principles of Internal Medicine, 22E
Step 5 - Learn Axis Determination (Quick Method)
Look at leads I and aVF:
| Lead I | Lead aVF | Axis |
|---|---|---|
| Positive (up) | Positive (up) | Normal (0° to +90°) |
| Positive (up) | Negative (down) | Left axis deviation |
| Negative (down) | Positive (up) | Right axis deviation |
| Negative (down) | Negative (down) | Extreme/indeterminate axis |
Step 6 - Learn the Major Patterns (in Order of Importance)
Start with the most clinically urgent patterns:
1. STEMI (ST elevation myocardial infarction)
- ST elevation in two or more contiguous leads
- Location tells you which artery: anterior (V1-V4 = LAD), inferior (II, III, aVF = RCA), lateral (I, aVL, V5-V6 = circumflex)
2. Arrhythmias
- Atrial fibrillation: irregularly irregular rhythm, no P waves, fibrillatory baseline
- Atrial flutter: sawtooth P waves at ~300 bpm, 2:1 or 4:1 block
- VT: wide complex tachycardia, rate > 100
3. Heart blocks
- 1st degree: PR > 200 ms, every P conducts
- 2nd degree Mobitz I (Wenckebach): PR progressively lengthens then drops a beat
- 2nd degree Mobitz II: PR fixed, random dropped beats
- 3rd degree (complete): no relationship between P waves and QRS
4. Bundle branch blocks
- RBBB: "RSR prime" (rabbit ears) in V1, wide S in V6. Mnemonic: WiRRoW (Wide R in Right, Wide S left in RBBB... use MaRRoW for RBBB, WiLLiaM for LBBB)
- LBBB: broad notched R in V5-V6, no septal Q waves
5. LVH and RVH
- LVH: S in V1 + R in V5 or V6 > 35 mm (Sokolow-Lyon criteria)
Step 7 - Practice Strategy
The single biggest factor in ECG competence is volume of practice. Here is a proven approach:
- Learn waveforms and normal values first (1-2 days)
- Read a focused textbook - Goldberger's Clinical Electrocardiography: A Simplified Approach is the gold standard reference (cited directly in Harrison's)
- Use free online cases - ECG Wave-Maven (Harvard/BIDMC) is a free self-assessment program with hundreds of real ECGs
- Read at least 1-2 ECGs daily - consistent daily exposure beats cramming
- Always read the clinical context - the patient's age, symptoms, and history shape interpretation
- Review your errors - keep a log of ECGs you misread and revisit them
Quick Reference: What to Say When Presenting an ECG
"This ECG shows a [rate] bpm, [regular/irregular] rhythm with [normal sinus/atrial fibrillation/etc.] rhythm. The PR interval is [normal/prolonged/short]. The QRS is [narrow/wide]. The axis is [normal/LAD/RAD]. There [are/are no] ST changes. There [are/are no] pathological Q waves. The T waves are [normal/inverted]. Overall impression: [diagnosis]."
This habit of presenting in a fixed order forces you to check everything and prevents errors of omission.
Sources: Harrison's Principles of Internal Medicine, 22E (2025); Goldberger's Clinical Electrocardiography, 10th Ed.
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