Prefixes in adjectives

In this lesson, students will look at some common prefixes that can be added to adjectives and see how they change meanings.


  • Identify some common prefixes in adjectives.
  • Describe the meanings contributed by common adjective prefixes.
  • Experiment with acceptable and unacceptable prefixes for particular adjectives.

Lesson Plan

The teacher explains that today, we will look at adjectives with distinctive prefixes.

There are many adjectives which don’t have particular recognisable prefixes (e.g. kind, sweet, dry). However, there are many others which do have distinctive prefixes. These typical prefixes can help us to identify them as adjectives.

In Slide 1 in the Activity page in the right hand menu, you will see some groups of adjectives which all have distinctive prefixes. Students should identify what kind of meaning these prefixes carry.

The students' task is to look at these adjectives and do as follows:

  • Identify all the typical adjective prefixes they can find in the examples.
  • For each adjective prefix, write down the other examples of adjectives with that prefix, taken from the list. Then try to think of several examples for each prefix which are not in the list. Students should see how many they an think of.
  • There may be some adjectives whose meaning is unfamiliar. Note down several of these and look them up in the dictionary.
  • Decide how do these prefixes change the meanings of the words they are added to.

You probably worked out that all of these prefixes have a negating (‘not’) meaning. For example, unofficial means ‘not official’ and disloyal means ‘not loyal’. You can see that these prefixes make a very significant change to meaning! They may be short but they have a powerful effect.

In Slide 2, we look at a puzzle using some different adjectives as root words. Which of our negative prefixes (un-, in-, non-, dis-) can we apply to these root words? Display Slide 2 on a smart board or projector. Drag a card to the right or left of another card to join them together. The other card should briefly flash. Double-click a joined card to separate it from the other one. You can ask for one or more clues if you wish, but you will not score points for these items.

Most of these words are 'fussy' about adding the prefixes: they allow just one, or one is much more usual. We don’t find, for example, distolerable or inhealthy

In Slide 3, we look at some variant forms. The negative prefix in- has variant forms. Compare the following (also displayed on Slide 3):


Students should consider the following questions:

  • What are the different variants? Can you see some patterns in where they occur?
  • What happens if we swap the different variants around between words?

We can work out the following:

  • There are other variants of the prefix spelt il-ir- and im-.
  • We get il- when the base word starts with lir- when the root word starts with r, and im- when the base word starts with m. The only sound added is the vowel sound, but an extra lr or is added to the spelling.
  • Did you try swapping with an in- in some of these examples? Do you find it easier to say irrelevant rather than inrelevantillegal rather than inlegal?
  • We also get im- when the base word starts with a sound made with the lips together, like p. For instance, we get impolite rather than inpolite. The sound is made with the lips together so it is less effort this way.

Then, in Slide 4, adjectives are displayed which can take a negative prefix. What would be the negative versions of the following words (also displayed on Slide 4)?


You can check your answers by pressing the buttons to see the answers on Slide 5.

So far we have looked at prefixes with negating meanings. However, there are a number of prefixes with other kinds of meanings that can be found in adjectives. Some of these can be seen in the groups of adjectives in Slide 6. Look at them and answer these questions:

  • Identify the different prefixes used in each group of words.
  • How do these prefixes change the meanings of the words they are added to?
  • For each prefix, see if you can think of two or three more adjectives beginning with that prefix.

You can check your answers about the prefixes and the kinds of meanings they add by pressing the buttons in Slide 7.

Further Discussion

What happens if we add our negative prefixes to the following common adjectives? Try it and see.

  • Did you think of examples like disweak and unbig? They sound very strange.
  • Can you think of a reason why we don’t add negative prefixes to these particular adjectives? (To answer this, think about how we express meanings like ‘not good’ and so on.)

These different prefixes have similar meanings. However, sometimes they create different shades of meaning in examples where more than one can be added to the same base word. For instance, look at these sentences with inhuman and non-human:

  • They were accused of cruel and inhuman treatment of the prisoners.
  • These chemicals are dangerous for both human and non-human life.

Could we swap the words around in these examples? Can you describe the difference in meaning between these two words?

The prefix un- is very commonly used and can be added to new words that come into the language. So sometimes alternative forms with un- may sound fairly acceptable, even if they are less usual. Did you notice any examples like this in the puzzle? One example might be unalcoholic: if someone said this instead of non-alcoholic, we would certainly know what they meant. Some base words do have more than one recognised possibility. An example (not in the puzzle) is advisableinadvisable is the usual form, but unadvisable is sometimes used instead, and is listed in some dictionaries.


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