Medical Terminology

How medical terms are built

Most medical words are assembled from a root together with a prefix, a suffix, or both. The root is the foundation of the word and carries its core meaning, and it usually cannot stand on its own. Cardi means heart and therm means heat, but neither is a word by itself.

To let a root join another word part, a vowel is attached to it, almost always an o. The result is a combining form: therm/o joined to meter gives thermometer. A compound word is a different construction again, two whole words joined together, as small and pox become smallpox.

A prefix is added to the front of a word and modifies its meaning, telling you what kind, where, in which direction or how many. Dys-, meaning difficult, placed in front of pnea, meaning breathing, gives dyspnea. A suffix is added to the end and completes the meaning: arthr, meaning joint, with -itis, meaning inflammation, gives arthritis.

Longer terms come apart the same way, one piece at a time. Cholecystitis is chol/e, meaning bile, plus cyst, meaning a closed sac, plus -itis, meaning inflammation. Put back together, it is inflammation of the closed sac that holds bile, which is the gallbladder.

Key roots / prefixes / suffixes (memorize)

A small stock of word parts accounts for most of the terms an EMT meets, and these are worth committing to memory outright. The roots name the structure, the prefixes qualify or place it, and the suffixes say what is happening to it.

• Roots: cardi (heart), gastro (stomach), hepat (liver), neur (nerve), nas (nose), or (mouth), and broncho, pulmo and pneumo (all of them lungs).
• Prefixes: brady- (slow), tachy- (fast), hyper- (above normal), hypo- (below normal), poly- (many), uni- (one), intra- (within), inter- (between), peri- (around), ante- and pre- (before), post- (after), contra- (against), dys- (difficult or painful), sub- (below), and super- and supra- (above).
• Suffixes: -itis (inflammation), -algia (pain), -emesis (vomiting), -pnea (breathing), -plegia (paralysis), -rrhea (discharge), -spasm (contraction), -ology (study of), -ist (specialist), and -ac and -al (pertaining to).

Abbreviations, acronyms & plain language

An acronym is an abbreviation that can be pronounced as a word, such as CPAP. Convenient as they are, abbreviations and acronyms are a recognized source of communication errors, and the risk is greatest in written documentation and at patient handoff, where the person reading what you wrote cannot stop and ask you what you meant. In those high-risk situations, plain language is the better practice. The common ones, such as CPR and EMS, are understood everywhere and remain fine to use.

The same caution applies with more force still when you are speaking with patients, with families and with children. Jargon they do not understand leaves them unable to answer your questions correctly: a patient asked whether they have ever had an MI may not recognize the term, while the same patient asked about a heart attack will answer at once. Whenever there is any potential for ambiguity or misunderstanding, use simple terms.

Anatomic position is the reference point everything else depends on

Anatomy is the study of the structure of the body, and physiology is the study of its function. Diffusion, the movement of a substance from an area of high concentration to an area of low concentration, is an example of physiology at work. Every directional term in medicine assumes a single starting point. In the anatomic position the body stands upright, faces forward and holds the palms forward, and that fixed frame of reference is what allows a word such as medial or anterior to mean the same thing every time, regardless of how the patient is actually positioned when you find them. Left and right always mean the patient's left and right.

Body planes

A plane is the flat surface produced by an imaginary slice through the body, and three of them are used to describe where something lies. The table below sets out each plane and the halves it divides the body into.

Table 5.1Body planes

The directional vocabulary is really just a handful of paired opposites

Directional terms come in pairs of opposites, and they are far easier to learn as pairs than one at a time. The table below gives each term and what it means.

Table 5.2The directional vocabulary is really just a handful of paired opposites

Reference lines exist because "the middle" needs a precise definition

The midline is an imaginary vertical line running down the center of the body, from between the eyes down to the navel, and it divides the body into right and left halves. The midaxillary line runs vertically down from the middle of the armpit, over the side of the chest and on down the flank of the abdomen, dividing the body front from back; it is the landmark used for assessing lung sounds and for needle decompression. The midclavicular line runs through the center of each collarbone and serves the same sort of precise, chest-based assessment. Lines drawn through the navel divide the abdomen into its four quadrants: right upper (RUQ), left upper (LUQ), right lower (RLQ) and left lower (LLQ).

Positional terms describe how the patient is actually lying, not directional relationships

One last group of terms describes the position the patient is actually lying in rather than the relationship of one body part to another. The table below sets out the positions you will describe most often.

Table 5.3Positional terms describe how the patient is actually lying, not directional relationships