English Reference

Word

monoxide

Phoneticsmonox·ide

US/məˈnɑksaɪd/

UK/mʌnˈɒksaɪd/

Definition

n. a chemical substance that has one oxygen atom in each molecule. You usually hear about it when people discuss carbon monoxide, a dangerous gas from car engines or heaters.

n. an oxide containing a single atom of oxygen per molecule. Frequently used in compound forms, most notably in reference to carbon monoxide.

Examples

“Carbon monoxide is a gas you cannot see or smell.”

“The landlord installed a detector to warn tenants about dangerous levels of carbon monoxide in the apartment.”

“While carbon monoxide is the most widely discussed variant due to its toxicity, other monoxides exist as stable chemical compounds in various industrial and geological contexts.”

Examples

simple

“Carbon monoxide is a gas you cannot see or smell.”

contextual

“The landlord installed a detector to warn tenants about dangerous levels of carbon monoxide in the apartment.”

complex

“While carbon monoxide is the most widely discussed variant due to its toxicity, other monoxides exist as stable chemical compounds in various industrial and geological contexts.”

Usage

Often used as part of a compound noun; uncountable when referring to the gas in general, but countable in specific chemical classifications.

Real-World Examples

“Researchers found strong evidence of carbon dioxide emission but no signs of water vapor or carbon monoxide, suggesting carbon dioxide is likely driving the centaur's activity.”
Phys.org · 1 Sept 2026
“Instead of releasing carbon dioxide emissions into the atmosphere, where the gas contributes to climate change, researchers want to capture and convert it into carbon monoxide .”
Phys.org · 1 Sept 2026
“These include that 3I has elevated levels of carbon monoxide, carbon dioxide and methane compared with solar system comets.”
Smithsonian Magazine · 29 Jun 2026

Etymology

Formed as mon- + oxide; compare the earlier dioxide, pentoxide, and tetroxide.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Domain

Chemistry

This entry

Level
C1 · Advanced
Frequency
Frequent
Updated

Scan code

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English Reference