prefix
Meaning of prefix: Change the front of a term and the organ stays the same while the meaning flips from too much to too little.
Definition of prefix
A prefix is a word part fixed to the front of a medical term to change its meaning, most often by describing amount, timing, position, direction or number. It cannot stand alone as a word. Prefixes carry no organ information themselves; that comes from the root, so the same prefix works across every body system.
Where does a prefix sit in a term?
At the front, ahead of the root that names the body part. Medical terms are assembled in a fixed order: prefix, then root, then suffix. Only the root is compulsory, and a great many terms carry no prefix at all. Because the prefix is read first, it frames everything that follows it. It never names an organ or a tissue itself. Instead it answers questions of degree, position, timing, direction or number: how much, where, when, which way, how many. The same prefix therefore moves freely between body systems, so hyper does identical work in front of a word about blood sugar, blood pressure or thyroid activity.
Which prefixes come in opposing pairs?
Most of the common ones arrive in twos, and learning the pair costs little more than learning one of them. Splitting a term at its prefix usually makes the whole meaning fall out, as it does with tachycardia, hyperglycemia and dysphagia.
| Prefix | Meaning | Root | Whole term |
|---|---|---|---|
| hyper | above normal | glyc, sugar | hyperglycemia, high blood sugar |
| hypo | below normal | glyc, sugar | hypoglycemia, low blood sugar |
| tachy | fast | card, heart | tachycardia, a fast heart rate |
| brady | slow | card, heart | bradycardia, a slow heart rate |
| dys | difficult or faulty | phag, swallowing | dysphagia, difficult swallowing |
| peri | around | cardi, heart | pericardium, the sac around the heart |
Why are prefixes so easy to mix up?
Several differ by a single letter while meaning opposite things. Hyper and hypo are the worst offenders, since one vowel separates too much from too little. Others sit close in meaning rather than in spelling: peri means around, para means beside, and pre means before in time or in place. A third group looks alike but comes from different sources, so a at the front means without, ab means away from, and ad means toward. Spelling also shifts to suit the letter that follows. Without appears as an before a vowel and as a before a consonant, which is why the blood word is anemia and the breathing word is apnea.
Also known as
Used in a sentence
The prefix tachy at the front of the term signals an abnormally fast rate.
Good to know
Hyper and hypo differ by one vowel while describing opposite states of the same measurement, which makes them the pair most often transposed in dictated and handwritten notes.
Word origin
Where “prefix” comes from
Prefix comes from the Latin praefixus, fastened in front, built from prae, meaning before, and figere, meaning to fasten.