ember

n. small piece of burning wood or coal

Embers are the glowing, hot coals made of greatly heated wood, coal or other carbon based material that remain after, or sometimes precede a fire. Embers can glow very hot, nearly as hot and sometimes as hot as the fire which created them. They radiate a substantial amount of heat long after the fire has been extinguished, and if not taken care of properly can rekindle a fire that is thought to be completely extinguished and can pose a fire hazard to anyone not careful.
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Noun
1. a hot glowing or smouldering fragment of wood or coal left from a fire
(synonym) coal
(hypernym) fragment

(n.)
A lighted coal, smoldering amid ashes; -- used chiefly in the plural, to signify mingled coals and ashes; the smoldering remains of a fire.
  

(a.)
Making a circuit of the year of the seasons; recurring in each quarter of the year; as, ember fasts.
  

Synonyms and related words:
alluvion, alluvium, ash, brand, burning ember, cinder, clinker, coal, deposition, deposits, diluvium, draff, dregs, dross, feces, firebrand, froth, grounds, lees, live coal, loess, moraine, offscum, precipitate, precipitation, scoria, scum, sediment, settlings, silt, sinter, slag, smut, soot, sublimate