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, 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

  • Discarded fruits and vegetables can quickly decompose, and thus add nutrients back to the soil.

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 fruits and vegetables must be rotting, then.

  • When candle wax is heated but not burned, the wax loses its solid structure and deforms because of the heat.

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


dis– the opposite of

  • When don’t actively decide where they will release seeds so that new plants can grow. Instead, plant seeds are randomly dispersed by some other agent other than the plants, 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.

  • Construction cranes can quickly be set up and are just as easily dismantled and removed.

If a big, tall machine that is used to lift heavy construction material is removed, it’s probably also taken apart. So the prefix dis- hints at the meaning of dismantled in this passage. Assembled construction cranes are put in a state opposite of assembled—they are taken apart.


inter- meeting or making contact

  • Interbedded with the rock sediment were thick, dark layers of iron deposits.

“Bedded” means “laid down.So if you understand the meaning of inter-, you can easily understand that the rock sediments and iron are laid down together.

  • Researchers recently hypothesized that one of the reasons dolphins swim next to each other (and not towards each other) is to avoid interference from each other’s sonar sounds and 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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  • David Recine

    David is a Test Prep Expert for Magoosh TOEFL and IELTS. Additionally, he's helped students with TOEIC, PET, FCE, BULATS, Eiken, SAT, ACT, GRE, and GMAT. David has a BS from the University of Wisconsin-Eau Claire and an MA from the University of Wisconsin-River Falls. His work at Magoosh has been cited in many scholarly articles, his Master's Thesis is featured on the Reading with Pictures website, and he's presented at the WITESOL (link to PDF) and NAFSA conferences. David has taught K-12 ESL in South Korea as well as undergraduate English and MBA-level business English at American universities. He has also trained English teachers in America, Italy, and Peru. Come join David and the Magoosh team on Youtube, Facebook, and Instagram, or connect with him via LinkedIn!