How the character is built
The 钅 radical marks this as a metal, and that is not a coincidence of this one character — it holds right across the table. Read the radical first and the element's state at room temperature is already settled. It is 金 (jīn) squeezed into the space beside another component — radicals change shape by position, which is why 金 is hard to spot until you know to look for 钅.
An ancient character rather than a coined one; it also means 'iron-clad, unshakeable' figuratively.
Where you actually meet it
地铁 (dìtiě) subway, metro; 铁路 (tiělù) railway
The element itself
The world's iron ore is, in the most literal sense, a fossil of the moment Earth's air changed. For a long stretch of the Precambrian the oceans held enormous quantities of dissolved iron, and as photosynthesis began releasing oxygen it precipitated out in fine alternating layers of iron oxide and silica — banded iron formations, hundreds of metres thick, and the source of nearly all the iron humans have ever used. Iron is also the most abundant element in the planet as a whole, most of it unreachable in the core, where its motion generates the magnetic field.
Where it sits among the 118
Iron is one of the fourteen elements that were known before anyone was keeping records of who found what.
In living things
Each red blood cell carries roughly 270 million haemoglobin molecules and each of those holds four iron atoms, every one of which exists to grab oxygen in the lungs and let it go again in the tissues. Iron is good at this because it sits comfortably in two oxidation states — which is also what makes it the workhorse of the cytochromes and iron–sulfur clusters that move electrons through respiration. The catch is availability: in oxygenated water iron rusts into essentially insoluble ferric hydroxide, so bacteria secrete siderophores that grip it with almost obsessive strength, and vertebrates fight back by binding their own iron up in transferrin and lactoferrin specifically to starve invaders of it.
In Chinese history and language
China was casting iron in blast furnaces while Europe still had only the bloomery, so cast ploughshares and thin-walled cooking pots were ordinary goods there centuries before they were anywhere else. The word carries that hardness into everything it touches — 铁面无私 tiěmiàn wúsī, "iron-faced and impartial", of an incorruptible official. And 铁饭碗 tiěfànwǎn, the iron rice bowl: the state job with its housing, clinic and pension, a bowl that could not be dropped or broken, which the reform era set about smashing. To call a job an iron rice bowl is still to say something precise about security and something faintly barbed about ambition.
Where it comes from in China
China's iron story starts at Anshan in Liaoning, where the ore is banded iron formation: dark magnetite alternating with pale quartz in fine layers, laid on a seafloor about two and a half billion years ago when the oceans still carried iron in solution and something — early photosynthesis, most likely — began stripping it out. Metamorphism has since baked those layers into a hard, glittering quartzite. It is lean ore, barely a third iron, and it has to be crushed and concentrated before it is worth putting near a furnace, which is part of why the country's steel industry runs so heavily on richer imported ore. The other great iron body, Bayan Obo north of Baotou in Inner Mongolia, is remembered for something else entirely — what came out of the ground alongside the iron.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
铁Iron in the dictionary →Others built the same way
Every one of these carries 钅, and every one is a metal.