used as a lubricant and as a moderator in nuclear reactors
"The engineers replaced the oil with graphite to serve as both a lubricant and a neutron moderator within the experimental reactor core."
An allotrope of carbon, consisting of planes of carbon atoms arranged in hexagonal arrays with the planes stacked loosely, that is used as a dry lubricant, in "lead" pencils, and as a moderator in some nuclear reactors.
"Graphite's unique structure makes it an effective dry lubricant for machinery while serving as the writing core in pencils and a neutron moderator in certain nuclear reactors."
In plain English: Graphite is a soft, dark gray form of carbon that feels slippery and leaves marks when rubbed against paper.
"She used her pencil to sketch a quick drawing on graph paper with graphite instead of ink."
Usage: Do not confuse "graphite" with "plumbago," an archaic synonym rarely used in modern technical or casual contexts. When referring to writing implements, specify "pencil lead" rather than using graphite alone for clarity.
The word graphite entered English via the German term Graphit, which was coined in 1789 by A.G. Werner to describe a mineral used for writing. This name ultimately traces back to the Ancient Greek verb meaning "to write."