Suffixes and Word Families
Prefixes get the drama — they can flip a word’s meaning — but suffixes do the quiet, structural work of English. The ending of a word usually tells you what kind of word it is: whether it names something, describes something, or tells how something happened. That is information you can use even when you have no idea what the rest of the word means.
Suffixes also explain why vocabulary study pays compound interest. You never really learn one word; you learn a root plus a set of endings, and suddenly you own the entire family.
A suffix is a word part added to the end of a root. Suffixes often change a word’s part of speech — predict becomes prediction, predictable, or predictably — and they add meanings such as “full of” (-ful), “without” (-less), or “inflammation” (-itis). A word family is the set of words built on one shared root.
Which suffixes should I learn first?
Sort them by the job they do. Noun suffixes name things; adjective suffixes describe; adverb suffixes tell how. The medical set at the bottom names conditions and specialties:
| Suffix | Makes a… | Meaning | Examples |
|---|---|---|---|
| -tion / -sion | noun | act or process of | prediction, decision, injection |
| -ity | noun | state or quality of | clarity, mobility, sterility |
| -ment | noun | result or means of | treatment, movement, judgment |
| -er / -or | noun | one who | teacher, donor, ventilator |
| -able / -ible | adjective | able to be | predictable, reversible, portable |
| -ful | adjective | full of | careful, painful, hopeful |
| -less | adjective | without | careless, painless, harmless |
| -ous | adjective | having, full of | cautious, infectious, nervous |
| -ly | adverb | in the manner of | carefully, rapidly, hourly |
| -ize | verb | to make or become | sterilize, stabilize, immunize |
| -ology | noun | study of | cardiology, dermatology, pathology |
| -ologist | noun | specialist in | neurologist, dermatologist |
| -itis | noun | inflammation of | dermatitis, tonsillitis, arthritis |
| -emia | noun | blood condition | anemia, hypoglycemia |
| -pathy | noun | disease of | neuropathy, cardiomyopathy |
How do suffixes change a word’s part of speech?
Watch one root move through a sentence’s different jobs:
- The lab results were hard to predict. (verb — the action)
- Her prediction turned out to be right. (noun — the thing)
- Fevers follow a fairly predictable pattern. (adjective — describes the pattern)
- The patient improved, predictably, after treatment. (adverb — tells how)
Test questions exploit this constantly: they ask which form of a word fits a blank. The meaning barely changes; the part of speech must match the sentence. If the blank needs a noun, only the -tion form will do.
What is a word family, and why should I study in families?
A word family is every word grown from one root: care, careful, careless, carefully, caregiver. Families are efficient to learn because the root meaning stays constant while the suffixes make predictable adjustments — and they are exactly how medical vocabulary is organized. From derm (skin) alone you get dermatology (the study of skin), dermatologist (the specialist), and dermatitis (inflamed skin), as the diagram above shows. Notice that -ful and -less build opposite family members: a painful procedure hurts, a painless one does not. One root, two endings, and you own both directions.
Worked examples: reading the ending
Example 1. “The wound showed no sign of ______.” Choices: infectious or infection. The blank follows “sign of,” which needs a noun — choose infection. The suffix -ion marks the noun; -ous marks the adjective.
Example 2. You meet nephropathy on a reading passage. Even if you have never seen nephr (kidney), the suffix -pathy tells you it is a disease of something — often enough to answer the question.
Example 3. Sterile is an adjective. Need the verb? Add -ize: sterilize. Need the noun for the state? Add -ity: sterility. The family assembles itself.
What is my suffix routine?
- Look at the word’s ending before anything else.
- Identify the part of speech the suffix creates: noun, adjective, verb, or adverb.
- Add the suffix’s meaning to the root’s meaning for a literal definition.
- For fill-in-the-blank questions, decide what part of speech the sentence needs first, then pick the form that matches.
- When you learn any new root, immediately build its family with two or three suffixes.
Watch: A Short Video Lesson
Khan Academy walks through this skill clearly in a few minutes. It is a helpful companion to the reading above:
Practice: endings and families
- What part of speech is mobility, and how do you know?
- Turn the adjective stable into a verb.
- What does tonsillitis mean, based on its suffix?
- Choose the correct form: “The nurse handled the situation ______ (careful / carefully).”
- Build the “without pain” member of the pain word family.
- A hematologist is a specialist in what, given that hemat means blood?
Answers
- A noun — the suffix -ity creates nouns meaning “state or quality of.”
- Stabilize — the suffix -ize means “to make.”
- Inflammation of the tonsils — -itis means inflammation.
- Carefully — the sentence needs an adverb telling how she handled it.
- Painless — the suffix -less means without.
- Blood — -ologist marks the specialist, so a hematologist specializes in blood.
Where this fits in your prep
This lesson completes the word-parts trio: start from common word roots, add common prefixes, and you can now decode from both ends of a word. Pair the skill with multiple-meaning words and the shades-of-meaning work in denotation and connotation to round out your vocabulary toolkit — and find every lesson in order at our English and language usage hub.
Recommended Prep Books
These study guides and practice books help you keep building momentum as you prepare:
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