Word formation: prefixes, suffixes, compounds
Building nouns, adjectives, adverbs and verbs with affixes, and forming compounds.
Word formation lets us build new words from a base (root) word by adding affixes or by joining words together. A prefix goes before the base and usually changes the meaning, especially the negative prefixes un-, in-, im-, ir-, il-, dis- and mis- (happy → unhappy, possible → impossible, regular → irregular, agree → disagree). A suffix goes after the base and usually changes the part of speech: -tion, -ment, -ness and -ity make nouns; -ful, -less and -able make adjectives; -ly makes adverbs; and -ise/-ise make verbs (decide → decision, happy → happiness, care → careful, quick → quickly, modern → modernise). A compound joins two words into one idea, written as one word (toothbrush), with a hyphen (well-known), or as two words (bus stop). In exams you must choose the right derivative AND spell it correctly, watching for spelling changes such as dropping a final 'e' or changing 'y' to 'i'. For example: from the verb 'decide' we form the noun 'decision', and from the adjective 'happy' we form the noun 'happiness' (y → i).
Key terms
| Suffix | Part of speech | Example |
|---|---|---|
| -tion | noun | produce to production |
| -ity | noun | responsible to responsibility |
| -ment | noun | move to movement |
| -ness | noun | kind to kindness |
| -ful | adjective | use to useful |
| -less | adjective | harm to harmless |
| -able | adjective | move to movable |
| -ly | adverb | quick to quickly |
| -ise | verb | modern to modernise |
| -en | verb | strong to strengthen |
| Prefix | Meaning | Example |
|---|---|---|
| un- | negative (not) | clear to unclear |
| in- | negative (not) | able to inability |
| im- | negative (before m/p) | possible to impossible |
| ir- | negative (before r) | regular to irregular |
| il- | negative (before l) | legal to illegal |
| dis- | negative (opposite) | agree to disagree |
| mis- | wrongly | read to misread |
- 1Start: Take the verb 'decide'.
- 2Add a suffix: Add the noun suffix -tion, but first watch the spelling: 'decide' drops the final 'e' and shifts to 'decis-'.
- 3Result: The noun is 'decision' (decide to decision).
- 1Look at the gap: He drove very ___ in the rain. The base word is 'careful'.
- 2Read the suffix: After a verb like 'drove', the gap needs an adverb, and -ly forms adverbs.
- 3Result: Add -ly to get the adverb 'carefully' (careful to carefully), not the noun 'carefulness'.
Pick the negative prefix by the first letter of the base: im- before m or p (impossible, immature), ir- before r (irregular), il- before l (illegal), un- or in- elsewhere. Do not write 'unpossible' or 'irmature'.
Choose the prefix the word actually takes: 'agree' goes with dis- (disagree), 'read' with mis- (misread), 'able' with in- (inability). Forms like 'misagree', 'unread' for 'read wrongly', or 'unability' are wrong.
Mind spelling changes when adding a suffix: drop a silent 'e' before a vowel suffix (move to movable), change 'y' to 'i' after a consonant (friendly to friendliness), and double a final consonant where needed (forget to unforgettable).
Let the suffix tell you the part of speech: -tion/-ment/-ness/-ity make nouns, -ful/-less/-able make adjectives, -ly makes adverbs, -ise/-en make verbs. A gap after 'to' needs a verb (strengthen), and a gap after a verb of manner needs an adverb (quietly).
Rules
- 1Negative prefixes change meaning, not part of speech: un- (unhappy), in-/im-/ir-/il- (incorrect, impossible, irregular, illegal), dis- (disagree), mis- (misunderstand).
- 2Choose the negative prefix by the first letter of the base: im- before m/p, ir- before r, il- before l, in- elsewhere (impolite, irresponsible, illogical, invisible).
- 3Suffixes usually decide the part of speech: -tion/-ment/-ness/-ity = noun, -ful/-less/-able = adjective, -ly = adverb, -ise/-ize = verb.
- 4Watch spelling changes: drop a silent 'e' before a vowel suffix (use → usable, decide → decision), and change 'y' to 'i' after a consonant (happy → happiness, beauty → beautiful).
- 5Compounds combine two words and may be written solid (toothbrush), hyphenated (well-known) or open (bus stop); the stress and meaning belong to the whole unit.
Practice
15 easy · 15 medium · 15 hard
10 random questions per test