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Mucus vs. Mucous

This article is about Mucus vs. Mucous — enjoy your reading!

  Angbeen Chaudhary  —  Grammar Tips
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The human body produces many fluids. Some of these fluids are mundane and some inspire disgust, but they are all necessary for the body’s daily operation and maintenance. One such fluid is found in many membranes in various places throughout the body, but it is most commonly seen dripping from or being sneezed out of someone’s nose. We have a word for this substance, but how should we spell it? Is mucous or mucus the correct spelling?

In this article, I will compare mucus vs. mucous. I’ll use each word in a sentence, and, at the end, I’ll show you a helpful trick to use to tell them apart.


The word mucous originated in mid-17th century from Latin word mucosus. The word mucus also originated in mid-17th century: from Latin.

Mucus as noun:

Mucus without the o, is used as a noun in English language where it refers to a slimy substance, typically not miscible with water, secreted by the mucous membranes and glands of animals for lubrication, protection, etc.

Because Callie did not cover her mouth when she sneezed, mucus flew into Shaw’s hair.

In certain medical contexts, a ball of mucus might be called a mucous ball. In this case, even though the ball itself is made up of mucus, mucous–not mucus–takes the function of an adjective. Mucous describes an attribute of the ball, therefore, a mucous ball and a mucous membrane.

Mucous as adjective:

The word mucous with an o is used as an adjective in English language where it means relating to, producing, covered with, or of the nature of mucus.

Mucus vs. Mucous

Dani had an infection in all her mucous membranes.


The tableware, the color of mucus and as bendable as a pocket watch in a Salvador Dali painting. [Fox News]

Between 0.5 and 5 mm, they live off the skin, blood and mucus of the host salmon. [Mayo News]

The warm water felt good against his cold mucous skin. [Village]

The syndrome is a rare, life-threatening disorder in which the skin and mucous membranes react severely to a medication or infection. [Minneapolis Star Tribune]

Mucus or mucous:

Mucus and mucous are so similar in spelling, and pronunciation that people sometimes mix them up. Mucous is an adjective. It describes certain membranes in the body. For example, a mucous membrane. Mucus is a noun. It refers to the fluid secreted by these membranes. Mucous is only an adjective, and mucus is only a noun. Mucous has the traditional -ous ending shared by many adjectives. Armed with this fact, you shouldn’t have trouble choosing mucus or mucous in your writing.

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