text: The Chinese compound  combines the common word   outside; exterior; external with   cinnabar; vermillion; elixir; alchemy. The antonym of  is   meaning inside; inner; internal, and the term   external elixir/alchemy was coined in connection with the complementary term  internal elixir/alchemy.
  The sinologist and expert on Chinese alchemy Fabrizio Pregadio lists four generally accepted meanings of : "The color cinnabar, scarlet, or light scarlet", "The mineral cinnabar, defined as a red stone formed by the combination of quicksilver and sulphur", "Sincerity (corresponding to  )", and "An essence obtained by the refining of a medicinal substance; a refined medicinal substance, the so-called medicine of the seekers of immortality for avoiding aging and death; a term often used for matters concerning the immortal". Pregadio concludes that the semantic field of the word dan evolves from a root-meaning of "essence", and its connotations include "the reality, principle, or true nature of an entity or its essential part, and by extension, the cognate notions of oneness, authenticity, sincerity, lack of artifice, simplicity, and concentration."
  The date for the earliest use of the term  is unclear. It occurs in Du Guangtings 901   (Explications Expanding on the Sages [Commentaries] on the Daodejing), which is quoted in the 978 Taiping guangji. Liu Xiyues  988   (Master Taixuan Langrans Poems on Advancing in the Dao) has the earliest mention of both the terms  and .'
    (Way of the Golden Elixir) was a classical name for  alchemy, and   (with  art; skill; technique; method) is the Modern Standard Chinese term.