Lesson 1: Common Prefixes for Opposites
Word Formation & Morphology (B1)
A powerful way to expand your vocabulary is to learn how to create opposites. Instead of learning two completely different words, you can often just add a small group of letters to the beginning of a word to change its meaning. These letter groups are called "prefixes". This lesson will teach you the most common prefixes used to create opposites.
Key Vocabulary
- Opposite A person or thing that is completely different from another.
- Prefix A group of letters added to the beginning of a word to change its meaning.
Prefix 1: "un-"
This is the most common prefix. It can be used with many different adjectives to mean "not".
- happy ➞ unhappy (sad)
- healthy ➞ unhealthy (bad for you)
- kind ➞ unkind (mean)
- comfortable ➞ uncomfortable
Prefix 2: "im-"
We often use im- before adjectives that start with the letters 'm' or 'p'.
- possible ➞ impossible
- patient ➞ impatient
- polite ➞ impolite
Prefixes 3 & 4: "ir-" and "il-"
These prefixes match the first letter of the adjective.
- We use ir- before adjectives that start with 'r': regular ➞ irregular
- We use il- before adjectives that start with 'l': legal ➞ illegal
Prefix 5: "in-" and "dis-"
These are also common, but their rules are less clear. You often need to memorize them.
- correct ➞ incorrect (wrong)
- formal ➞ informal
- honest ➞ dishonest
- agree ➞ disagree (This is a verb!)
Usage Note: There is no "Perfect" Rule
While the rules for 'im-', 'ir-', and 'il-' are quite strong, the choice between 'un-', 'in-', and 'dis-' can be tricky. The best strategy is to notice these words when you read, and when you learn a new adjective, check a dictionary to see if it has a common opposite with a prefix.
In Conversation
Bora is telling Srey about a bad day at work.
Bora: I had a bad day. I had to talk to an impolite customer who was very impatient.
Srey: Oh no. It's very uncomfortable to deal with rude people.
Bora: Yes. And I made an incorrect calculation on a report. It was an irresponsible mistake.
Srey: Don't worry, everyone makes mistakes. It's not impossible to fix it.
Bora: I know. I just disagree with my boss's reaction. He was very unkind.
Srey: Well, I am sure tomorrow will be a better day.
Check Your Understanding
- What is the opposite of 'possible'?
- a) unpossible
- b) impossible
- c) dispossible
Answer: b) impossible (The 'im-' prefix is used before 'p').
- What is the opposite of 'regular'?
- a) irregular
- b) inregular
- c) unregular
Answer: a) irregular (The 'ir-' prefix is used before 'r').
- If something is 'illegal', it is ______.
- a) not legal
- b) very legal
- c) a little legal
Answer: a) not legal
Your Mission
- My Opposites: Complete these sentences with the correct opposite form: "It is ______ (polite) to shout in a library. My handwriting is ______ (regular). That story was ______ (logical)."
- Notebook Practice: Go to your vocabulary notebook. Find three adjectives you already know. Use an online dictionary to see if they have an opposite with a prefix. If yes, add it to your notebook.
- Speak: Your mission is to use one word with an opposite prefix in a conversation today. (e.g., "This chair is very uncomfortable." or "It is impossible to work with all this noise.")