Word Choice: Defuse vs. Diffuse

One common mistake we see at Proofed is similarly spelled words being confused with one another. This seems to happen more often when one word is a little obscure, such as with ‘defuse’ and ‘diffuse’.

Although not a term you might use every day (unless you’re a bomb disposal expert), ‘defuse’ is in the vocabulary of most native English speakers. The word ‘diffuse’, however, is a bit less common, which means that people are more likely to misuse it.

They get mixed up sometimes because they look similar on the page, yet their meanings differ significantly and confusing ‘defuse’ and ‘diffuse’ can severely impair your ability to communicate ideas effectively. But sorting out linguistic confusions is why we’re here! Thus, in this post we set out everything you need to know about how to use ‘defuse’ and ‘diffuse’.

Defuse (Make Less Dangerous)

The verb ‘defuse’ is easy to master, as it combines the prefix ‘de-’ (meaning ‘undo’) with the noun ‘fuse’ (in this context, the trigger from an explosive). The literal definition of ‘defuse’ is simply ‘to disarm an explosive’:

Luca had never failed to defuse a bomb before, but this time his hands were shaking…

A second figurative meaning of ‘defuse’ is simply ‘make something less dangerous’. For instance, we might say:

You could have cut the tension with a knife, but the smooth-talking Emma soon defused the situation.

Diffuse (Spread or Scatter)

The word ‘diffuse’ can be used as either a verb or an adjective. When used as a verb, its primary meaning is to spread, scatter or disseminate:

The internet is a powerful tool for diffusing information .

The smoke had diffused throughout the room.

In the sciences, ‘diffuse’ can also mean ‘undergo diffusion’. This refers to the movement of molecules from an area of high concentration to one of lower concentration. For example, we might say:

When the dye is added to the water it quickly diffuses.

When used as an adjective, meanwhile, ‘diffuse’ simply means that something is widely or thinly spread. So we could also say:

The diffuse light shone through the frosted window.

A related use is to mean ‘wordy’ or ‘unclear’ when describing speech or writing. These are ‘thinly spread’ words, so to speak:

The PM’s speech was diffuse, and many in the audience feel asleep.

Defuse or Diffuse?

As long as you remember that to ‘de-fuse’ means to remove danger (whether figuratively or by actually disarming a bomb) it should be fairly simply to know which word to use in any given situation:

  • If you’re discussing a dangerous/tense situation or an explosive device, the word to use will be ‘defuse’.
  • On the other hand, if you’re writing about something which is spread out or distributed over a large area, the word you need is ‘diffuse’.
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