Commonly Confused Prefixes in Medical Terminology

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  • 0:35 AB- & AD-
  • 1:41 ANTE- & ANTI-
  • 2:38 BRACHY- & BRADY-
  • 3:27 HEMI-, PARA- & SEMI-
  • 4:48 INTER- & INTRA-
  • 5:34 PERI- & PRE-
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

This lesson will go over the most commonly confused medical prefixes. We will look at how the prefixes are used and go over examples to help distinguish them from each other.

Confusing Medical Prefixes

There are an enormous number of medical prefixes that you have been exposed to at this point. Most of them may be sticking okay, but there are likely a few that you keep getting confused. You are not alone!

There are some prefixes that most healthcare professionals have to take an extra minute to think about in order to keep them straight. This could be because they are spelled or sound similarly, or it could be because the meanings are close but not quite the same. We are going to look at those prefixes and how they are used now.

Ab- and Ad-

Our first two commonly confused prefixes are opposites of each other, even though they only differ by one letter.

The prefix ab- means 'away from.' You may be thinking that it looks familiar since the word 'abduction' starts with the same prefix. This is a good start. Remember that a person who is abducted is taken away from where he or she belongs. In medical terminology, this is used when describing what is happening with one part of the body in relation to another part of the body. For example, if you raise your arm, then what you did was abduct the arm away from the trunk of the body.

The prefix ad- means 'toward' or 'increase.' Think about what happens when you add. You are putting things towards each other and/or increasing what is there. The same is true in medical terminology. You can lower your arm to move it toward the body. The term for this is 'adduct,' meaning 'toward the trunk of the body.'

Ante- and Anti-

Our next two prefixes look similar to each other but are not related at all.

Ante- is a prefix that means 'before' or 'in front of.' It is used to tell the location of something in the body in relation to another part of the body. Most commonly, you will see the term 'antecubital,' which means 'in front of the elbow.' This is where blood is drawn from the body.

You may have had a day that you really didn't feel like being bothered with other people and someone may have told you that you were being 'antisocial.' This term uses the prefix anti-, meaning 'against.' That day, you were 'against socializing.' In medical terminology, you will most likely see this being used to describe medications, such as 'antibiotics' or 'antiviral' drugs, meaning 'against bacteria' and 'against viruses,' respectively.

Brachy- and Brady-

The next confusing set of prefixes is rarely seen outside of medical terminology.

The prefix brachy- means 'short' or 'little.' This is used to describe when something is abnormally little in the body. It is also used for when something is abnormally short. A person who is only taking short breaths may be termed as having 'brachypnea,' meaning 'short breaths.'

Another possibility for what could be happening with the person's breathing is that he or she is having 'bradypnea,' meaning 'slow breathing.' The prefix in this term is brady-, which means 'slow.' This prefix is used in terms to describe when something is happening slower than the normal rate.

Hemi-, Para- and Semi-

The meanings of our next set of prefixes are close, but we must take a little time to distinguish their subtle differences.

Both hemi- and semi- mean 'half.' There is a difference in how they are used though. Hemi- is normally used to signify half of the body or some part of the body. This is seen in the term 'hemiparesis,' which means 'paralysis of half of the body.' On the other hand, semi- is used to describe things that are happening with the body, such as in the term 'semiconscious,' which means 'half conscious.'

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