CO2, the chemical formula for carbon dioxide, has been added to the Oxford English Dictionary, with experts saying it is so commonly used that it deserves its own entry.
The OED's custodians have added a number of climate-related words to the dictionary in the run-up to the Cop26 conference in Glasgow, which begins at the end of this month.
Soaring carbon dioxide emissions have been a major driver of global warming since the industrial revolution. The gas is produced in vast quantities by the burning of fossil fuels and other polluting processes.
Controlling CO2 levels has been a goal of governments, environmentalists and scientists for decades since its warming impact was realised. There is perhaps no other chemical formula that is more well-known, with only water (H2O) challenging for the crown.
Other climate-related words set to be included in the dictionary for the first time include "eco-anxiety", "global heating" and "climate sceptic".
"We will often give the formulae for compounds that are included in the OED, and typically they would appear at the fuller form of the relevant term – H2O appears within the definition for water, for example, rather than as a headword entry in its own right. The same is true for oxygen itself," Trish Stewart, the OED science editor, told The Telegraph.
"CO2 is in frequent general use and acts more like a word than a formula or abbreviation, especially in forming compounds. People talk about CO2 emissions more than they talk about carbon dioxide emissions – but you rarely, if ever, hear of an H2O shortage."
CO2 will be added to the dictionary as a true new entry and will have its own headword slot, joining H2O as the only chemical formula to get this recognition.
Ms Stewart added: "As world leaders come together to seek solutions to the climate change problem, it has been fascinating, if at times somewhat alarming, to delve deeper into the language we use, both now and in the past, to talk about climate and sustainability.
"The very real sense of urgency that is now upon us is reflected in our language. What happens next depends on so many factors, but one thing we can be sure of is that our language will continue to evolve and to tell the story."