What Are Prefixes and How Do They Change Adjectives?

A prefix is a group of letters added to the beginning of a word. It changes the word’s meaning.

When we add a negative prefix to an adjective, it usually creates an antonym – a word with the opposite meaning. Think of it as adding ‘not’ or ‘the opposite of’ to the original adjective.

• For example, possible means ‘can happen’. Add im-, and it becomes impossible, meaning ‘cannot happen’.
• Another example is successful, meaning ‘achieving a desired result’. With un-, it becomes unsuccessful, meaning ‘not achieving a desired result’.

Common Negative Prefixes in English

There are several common prefixes that make adjectives negative. While there are some general rules, often you need to learn which prefix goes with which adjective.

• Un-: This is the most common negative prefix. It can be added to many adjectives. For example: unhappy, unbelievable, unsinkable.
• In-, Im-, Il-, Ir-: These prefixes are variations of the same idea (‘not’). The choice depends on the first letter of the adjective:
  • Im- is used before adjectives starting with m or p. Examples: impossible, impolite, improbable.
  • Il- is used before adjectives starting with l. Examples: illegal, illegible.
  • Ir- is used before adjectives starting with r. Examples: irregular, irrelevant.
  • In- is used before many other adjectives, especially those starting with c, d, e, a. Examples: inactive, incomplete, indecisive, incredible.
• Dis-: This prefix also means ‘not’ or ‘the opposite of’, often implying a lack of something. Examples: dishonest, disagreeable, disloyal.

Why Is It Important to Learn These Prefixes?

Learning adjectives with negative prefixes is a powerful way to expand your B2 vocabulary efficiently. Instead of learning two separate words (e.g., ‘happy’ and ‘sad’), you learn a base word and how a prefix can create its opposite.

• Understanding Nuance: It helps you grasp subtle differences in meaning. For instance, uninterested (not interested) is different from disinterested (impartial, unbiased).
• Reading Comprehension: You can often guess the meaning of an unfamiliar adjective if you know its base word and the meaning of the prefix.
• Speaking and Writing Fluency: Using these adjectives correctly makes your English sound more natural and precise.

Examples

• The movie was so unbelievable that I couldn’t enjoy it.
• It’s impossible to finish this project in one day.
• Her excuse for being late was completely irrelevant to the discussion.
• The company’s first attempt was unsuccessful, but they tried again.
• He was disloyal to his friends by sharing their secrets.
• Parking here is illegal, so you might get a fine.

Practice

Common mistakes for Spanish speakers

Spanish speakers sometimes make mistakes with negative prefixes due to direct translation or confusion between similar-sounding prefixes.

• Using the wrong prefix: A common error is using in- where un- is needed, or vice-versa. For example, saying *inhappy instead of unhappy, or *undecisive instead of indecisive.
• Direct translation of ‘un-‘: Sometimes, Spanish speakers might try to use in- for all negative meanings, similar to Spanish ‘in-‘. Remember the specific rules for im-, il-, ir-, and the widespread use of un-. For instance, *inpossible is incorrect; it should be impossible.
• Forgetting the prefix rules: It’s easy to forget that im- goes with ‘m’ or ‘p’, il- with ‘l’, and ir- with ‘r’. For example, *inpolite is wrong; it’s impolite.

Frequently asked questions

Can all adjectives take a negative prefix?

No, not all adjectives can take a negative prefix. For example, we don’t say *ungood or *inbad. For these, we use different words like bad or not good. You need to learn which adjectives commonly combine with prefixes.

Are there other types of prefixes for adjectives?

Yes, besides negative prefixes, there are prefixes that indicate repetition (like re- in reusable), time/order (like pre- in pre-cooked), or degree (like super- in super-fast). However, negative prefixes are among the most common and useful for B2 learners.

How can I remember which negative prefix to use?

The best way is through consistent exposure and practice. Read a lot, pay attention to new words, and try to use them in your speaking and writing. Flashcards can also be helpful. Remember the basic rules for im-, il-, ir-, and know that un- is very common.

How are adjectives with negative prefixes useful for B2 exams?

For B2 exams, understanding adjectives with negative prefixes is vital for vocabulary sections, reading comprehension, and listening tasks. You might encounter questions where you need to identify antonyms or choose the correct word to complete a sentence, often involving these prefixes. It helps you understand nuanced meanings and improves your overall lexical range.