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Prefixes de-, dis-, and inter- on the TOEFL

In a recent post, we looked at the meanings of the English prefixes de-, dis-, and inter-. These prefixes are very important on the TOEFL, because they can help you guess at the meanings of unfamiliar academic words.

In this post, we’ll review the meanings of these three prefixes. For each prefix, we’ll also look at examples of these prefixes on the TOEFL, with tips on how to use prefixes to as clues to the definitions of TOEFL vocabulary words.


de- to get rid of something or reduce it to a smaller quantity

  • TOEFL Example 1 (from Official TOEFL iBT Tests, Volume 1, page 28):
    The organic matter may partially decompose, using up the dissolved oxygen in the sediment.

You can know that de- means to lose something or a portion of something, so you may be able to guess that decompose means “to lose composition.” The organic matter must be rotting, then.

  • TOEFL Example 2 (from TOEFL Quick Prep Volume 2, page 20): But ice is also plastic—it can change shape without breaking. If you leave, for example, a bar of ice supported only at one end, the end—the unsupported end— will deform under its own weight—it’ll kind of flatten out at one end, get distorted, deformed.

And here, you can correctly guess that deform means to lose one’s form or to have one’s form grow smaller. So the ice is losing its shape and shrinking as it melts.


dis– the opposite of

  • TOEFL Example 1 (from TOEFL Quick Prep Volume 4, page 38):
    Like plants, for example— they don’t make active choices about where to grow—they’re dispersed by some other agent, like the wind.

This one’s a little tricky. But you can use your prefix knowledge to guess that plants change from one state to an  opposite state. And with wind doing the dispersing, you can specifically guess that plants go from being all in one place to an opposite state—being spread around.

  • TOEFL Example 2 (from Official TOEFL iBT Tests, Volume 1, page 28):
    Now portable drilling machines are set up and are then dismantled and removed.

If a machine that is fixed into the ground and drills into it is removed, it’s probably also taken apart. So the prefix dis- hints at the meaning of dismantled in this passage. Assembled drilling machines are put in a state opposite of assembled—they are taken apart.


inter- meeting or making contact

  • TOEFL Example 1 (from TOEFL Quick Prep Volume 2, page 10): Interbedded with the salt were thin layers of what appeared to be windblown silt.

“Bedded” means “laid down.So if you understand the meaning of inter-, you can easily understand that the salt and windblown silt are laid down together.

  • TOEFL Example 2 (from The Official Guide to the TOEFL Test, page 422): And there’s this theory that one reason dolphins swim side by side is to avoid interference from each other’s sonar clicks.

“Ference” isn’t really a word on its own. But with the prefix inter- before it, it’s pretty clear that interference refers to sonar sounds bouncing off of each other.


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