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Language Arts

Diffuse vs. Defuse

Defuse versus Diffuse - learn the differences in this article about two words that are often confused. Definitions of diffuse and defuse are included, as well as tips on how to remember the difference between diffuse and defuse.

Diffuse vs. Defuse

A speech full of diffuse ramblings is not likely to defuse the palpable tension in this crowd of hungry people. These two similarly spelled and similarly or identically pronounced, but etymologically unrelated words have confused many. Here’s the scoop on keeping them straight.


Diffuse is both a transitive verb (one that takes an object), an intransitive verb (one that works without an object), and an adjective. As a verb, diffuse has meanings related to spreading out.

Transitive verb: After the addition of “fog juice,” the fog machine diffused “theatrical smoke” across the stage set.

Intransitive verb: Cigarette smoke diffused through the room.

As an adjective, diffuse has meanings related to a lack of focus, but literal, physical spreading out as well as figurative lack of focus in discourse. In the latter case, the discourse may be wordy, poorly organized, or not cogent, given the purpose for which it was intended.

Literal: The interior designer’s diffuse lighting design didn’t work especially well for the office situation: many employees were complaining of headaches and eye strain.

Figurative: The defense attorney’s closing argument was diffuse and ineffective.

Diffuse came into English in the fifteenth century through Middle English from the Latin word diffundere meaning “to spread out” (from dis• meaning apart and fundere meaning to pour). It has distinct pronunciations for its verb form and its adjective form. As a verb, it is pronounced /dih FYOOZE/ with a final /z/ sound, while as an adjective, it is pronounced /dih FYOOSE/ with a final /s/ sound.


Defuse is a transitive verb, the origin of which some sources date to 1943, when it was presumably “created” by adding the prefix de• to the verb fuse to refer to the literal removal of a fuse from a bomb during World War II. It is also used figuratively in regard to relieving or dispelling tension in a difficult situation or reducing something’s power or influence.

Literal: The bomb squad was able to defuse the letter bomb intended for the controversial senator.

Figurative: I defused the argument between my brothers by getting them to taste-test my new recipe for apple pie.

Defuse is based on the prefix de• meaning “the opposite of” and the verb fuse, “to create a fuse,” which came into English from the Italian word fuso, meaning “spindle,” on account of the original fuse shape. It’s ultimate origin the Latin form fusus. Defuse is pronounced /dee FYOOZE/, so you can see that it has only a slightly different sound than the verb diffuse (the vowel in the first syllable).

Remembering the Difference

Perhaps the double f in the middle of diffuse can remind you that it’s the word that refers to spreading, while defuse, with the word fuse (no extra letters in it), is the one about taking out the fuse or reducing danger.

Written by Mary Elizabeth