October 2026 - Affixes: Prefixes & Suffixes Study Guide

The three parts of a word

• Root — the core carrying the basic meaning. Cardi means heart.
• Prefix — attached at the front, usually changing meaning. Brady- means slow.
• Suffix — attached at the end, usually changing the part of speech, and in clinical terms often naming a condition or procedure. -ia marks a condition.
• Put together: brady + cardi + a = the condition of a slow heart.

Prefixes that recur in clinical language

Suffixes worth knowing

Suffixes change the part of speech

Outside clinical vocabulary, a suffix's main job is grammatical. -tion and -ment make nouns (document → documentation, treat → treatment), -ful and -ous make adjectives (care → careful), -ly usually makes an adverb, and -ise or -ify make verbs.

That is often what the question is really asking. When a sentence needs a noun and the choices are advise, advice, advisory and advisable, the grammar decides it before any question of meaning arises.

Decoding an unfamiliar word

Terms to know

Affix

A prefix or suffix attached to a root.

Prefix

An affix at the front of a word.

Suffix

An affix at the end of a word.

Root

The core of a word, carrying its basic meaning.

Derivation

Making a new word by adding an affix.

Part of speech

The grammatical category a suffix often determines.

What the HESI asks most

The same core ideas appear in different wording. If you can answer these without stopping to think, you have what this section requires.

Key points

• Prefixes change meaning; suffixes usually change part of speech or name a condition.
• hyper- is above, hypo- is below; brady- is slow, tachy- is fast.
• -itis is inflammation, -ectomy is removal, -ology is the study of.
• Break an unfamiliar word into prefix, root and suffix.
• When the choices differ only by suffix, the grammar of the sentence decides.