丹 originally referred to cinnabar, a red mineral used in traditional alchemy (炼丹). It later extended to mean 'pill/elixir' and the color red. It also appears in many place names like 丹麦 (Denmark).
Components
pictograph
丹dān
cinnabar; red
Pictograph of a mining shaft or mortar with a dot of cinnabar (mercury sulfide, the bright red mineral) inside. The frame is the well, the dot is the precious red ore. From this concrete sense came 'cinnabar red,' then 'red' generally and 'pill/elixir.' Filed under Kangxi #3 丶 (diǎn, dot) — the central dot.
Filed under radical 丶 (diǎn, #3) by convention. 丶 is not a separate component in 丹, so no strokes are highlighted.
