In English, we can change a word from positive to negative by adding a prefix. 'Happy' becomes 'unhappy' (not happy). 'Agree' becomes 'disagree' (not agree). 'Correct' becomes 'incorrect' (not correct). 'Possible' becomes 'impossible' (not possible). 'Regular' becomes 'irregular' (not regular). 'Stop' becomes 'non-stop' (without stopping). Each prefix has rough rules about which words it goes with. UN- is the most common — used with adjectives (unhappy, unlucky) and some verbs (undo). DIS- is used with verbs (disagree) and some adjectives (dishonest). IN-, IM-, IR-, IL- are different forms of the same prefix that means 'not' — IM- before m and p (impossible, immortal), IR- before r (irregular), IL- before l (illegal), IN- before other letters (incorrect, invisible). NON- is more general — often used with hyphens (non-stop, non-smoker). Students who know the rules can build many negative words from positive ones. This lesson is the negative-focused version of the prefixes lesson (#13).
Before you start — think honestly about your own teaching and experience.
Look at the examples. Answer each question before reading the explanation — this is how your students will learn too.
happy → unhappy (not happy)
lucky → unlucky (not lucky)
fair → unfair (not fair)
kind → unkind (not kind)
able → unable (not able)
known → unknown (not known)
employed → unemployed (not employed)
UN- works with many words. What kinds of words does it go with?
UN- is the most common negative prefix in English. It works with adjectives most often (unhappy, unlucky, unable, unknown). It also works with some past participles (unemployed = not employed) and some nouns (unknown). UN- is the safe default for adjectives — when students do not know the right prefix, UN- is often correct. The rule: UN- + word, no spelling change. The word stays exactly the same; UN- just attaches to the front. Some words take only UN- (unhappy — never 'inhappy', 'dishappy'). Drilling UN- with common adjectives builds a strong base. Other prefixes (DIS-, IN-) work with different sets of words.
DIS- (often with verbs and some adjectives):
agree → disagree (not agree)
appear → disappear (no longer appear)
like → dislike (not like)
honest → dishonest (not honest)
respectful → disrespectful (not respectful)
IN- / IM- / IR- / IL- (different forms of the same prefix):
correct → incorrect (not correct)
possible → impossible (not possible — IM before P)
regular → irregular (not regular — IR before R)
legal → illegal (not legal — IL before L)
NON- (more general — often with hyphens):
stop → non-stop (without stopping)
smoker → non-smoker (a person who does not smoke)
standard → non-standard (not standard)
Which words go with which prefix? Why does English have so many negative prefixes?
[POINTS IT CONSIDER: Each prefix tends to go with specific kinds of words. DIS- often goes with verbs (disagree, disappear, dislike) and some adjectives (dishonest, disrespectful). IN- (with its variants IM-, IR-, IL-) tends to go with words from Latin — formal or academic words. The variant depends on the next letter: IM- before P or M (impossible, immortal), IR- before R (irregular), IL- before L (illegal), IN- before other letters (incorrect, invisible, inactive). NON- is more general and often used with hyphens — for compound negatives (non-stop, non-smoker, non-standard). Students cannot always predict which prefix to use — they must learn each negative word individually. But knowing the patterns helps. The key error to watch: do not just guess. UN- works with many adjectives. DIS- works with many verbs. IN- and variants work with Latin-origin words.]
IM- before P or M:
possible → impossible (not 'inpossible')
polite → impolite
perfect → imperfect
mortal → immortal
moral → immoral
IR- before R:
regular → irregular (not 'inregular')
responsible → irresponsible
relevant → irrelevant
IL- before L:
legal → illegal (not 'inlegal')
logical → illogical
literate → illiterate
Why are there different forms? What is the rule?
IM-, IR-, IL- are not different prefixes — they are spelling variants of IN-. The rule is about pronunciation. Saying 'inpossible' is hard because the n and p sounds are different — so the n changes to m to match the p. Saying 'inregular' is hard because n and r are different — so the n changes to r. Saying 'inlegal' is hard for the same reason — so the n changes to l. The pattern: IN- changes its last letter to match the first letter of the word that follows. Before P or M, IN becomes IM. Before R, IN becomes IR. Before L, IN becomes IL. Before other letters (vowels and most consonants), IN stays as IN: incorrect, invisible, inactive, indirect. Students who know this rule can predict the spelling of new negative words.
| Prefix | Used with | Examples | Notes |
|---|---|---|---|
| un- | Adjectives, some verbs | unhappy, unlucky, unfair, unable, unknown, unkind, unemployed, undo, unlock | Most common. Default for many adjectives. |
| dis- | Verbs, some adjectives | disagree, disappear, dislike, disconnect, dishonest, disrespectful | Often for verbs. The dis- often suggests reversing or undoing. |
| in- | Latin-origin words (default form) | incorrect, invisible, inactive, indirect, informal, inability | Used before vowels and most consonants. |
| im- | Words starting with P or M | impossible, impolite, imperfect, immortal, immoral, immature | IN changes to IM before P or M. |
| ir- | Words starting with R | irregular, irresponsible, irrelevant, irrational | IN changes to IR before R. |
| il- | Words starting with L | illegal, illogical, illiterate, illegible | IN changes to IL before L. |
| non- | General — often with hyphens | non-stop, non-smoker, non-standard, non-fiction, non-violent | More general. Often suggests 'without' rather than 'opposite of'. |
| Common errors | Wrong combinations | inhappy ✗ (unhappy), unpossible ✗ (impossible), inregular ✗ (irregular), unagree ✗ (disagree) | Each negative word goes with one specific prefix. Memorise common words. |
PATTERN 1 — UN- is most common: For most negative adjectives, UN- is the safe default. Unhappy, unlucky, unfair, unable, unknown. Just add UN- to the start with no spelling change. Drilling common UN- words builds a strong base.
PATTERN 2 — DIS- is often for verbs: Many negative verbs use DIS-. Disagree, disappear, dislike, disconnect, disregard. The DIS- often suggests reversing or undoing. Also some adjectives — dishonest, disrespectful.
PATTERN 3 — IN- and its variants: IN- is for Latin-origin words. Before most letters, it stays as IN- (incorrect, invisible). Before P or M, it changes to IM- (impossible, immortal). Before R, it changes to IR- (irregular). Before L, it changes to IL- (illegal). The change is for pronunciation.
PATTERN 4 — NON- is more general: NON- often suggests 'without' or 'not having' rather than 'opposite of'. Non-stop (without stopping), non-smoker (without smoking), non-fiction (not fiction). Often used with hyphens, especially in compound nouns.
PATTERN 5 — Each word goes with one prefix: Students cannot guess freely. Each negative word goes with one specific prefix. Happy → unhappy (not 'inhappy' or 'dishappy'). Possible → impossible (not 'unpossible'). Regular → irregular (not 'unregular'). Memorise common words.
PATTERN 6 — Some patterns help: Adjectives ending in -ed often take UN- (unemployed, unfinished, unknown). Verbs often take DIS- (disagree, disappear). Latin-origin formal words often take IN- variants (incorrect, impossible, irregular). The patterns are not absolute but they help.
PATTERN 7 — Common errors: 'Inhappy' (wrong — should be unhappy). 'Unpossible' (wrong — impossible). 'Inregular' (wrong — irregular). 'Unagree' (wrong — disagree). Each error signals the student does not know the right prefix for that word. Drill the common negative words to fix this.
Negative prefixes are powerful word-building tools. Once students know that 'happy' becomes 'unhappy', they have access to a full set of negative words. Cultural context: English has many negative prefixes because the language has borrowed from Latin (in-, im-, ir-, il-) and German/Old English (un-, dis-) over centuries. The variety reflects this history. The lesson connects to the prefixes lesson (#13) — broader treatment — and to suffixes (#15, #28, #33) — word-building patterns. Together they cover the main word-building tools.
Build a negative-prefix wall with the most common pairs. UN-: happy/unhappy, lucky/unlucky, fair/unfair. DIS-: agree/disagree, like/dislike, appear/disappear. IN- and variants: correct/incorrect, possible/impossible, regular/irregular. Add words as students meet them. Drill the common pairs until they are automatic.
Choose the correct negative form of each word. Apply the rules of which prefix goes with which word.
Each sentence has a wrong negative prefix. Find the wrong word, write the correct one, and explain.
Use this sequence directly in class — guided discovery, no textbook needed. Tap each step to mark it done.
STEP 1 — Why negative prefixes (5 min): Show that English builds negatives by adding prefixes. Happy → unhappy. Possible → impossible. Establish that there are several prefixes and each goes with specific words. Knowing the rules helps students build many negative words.
STEP 2 — UN- is the default (5 min): Drill UN- with common adjectives. Unhappy, unlucky, unfair, unable, unkind, unknown. Show that UN- is the most common and works with many words. Just add UN- to the start.
STEP 3 — DIS- for verbs (6 min): Drill DIS- with common verbs. Disagree, disappear, dislike, disconnect. Plus some adjectives — dishonest, disrespectful. DIS- often suggests reversing or undoing. Many negative verbs take DIS-.
STEP 4 — IN- and its variants (8 min): Drill IN-, IM-, IR-, IL- as variants of one prefix. IN- (incorrect, invisible). IM- before P or M (impossible, immortal). IR- before R (irregular). IL- before L (illegal). Show why the variants exist (pronunciation). Drill examples of each.
STEP 5 — Match prefix to word (4 min): Give students a list of positive words. They must produce the negative form using the right prefix. Happy → unhappy. Possible → impossible. Agree → disagree. Regular → irregular. Smoker → non-smoker. Drill until automatic.
Use directly in class — copy, adapt, or read aloud. No printing needed.
For each strategy, choose the option that best describes where you are now.
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