A cewar ƙamus, Carbonic acid rauni ne, acid mara ƙarfi (H2CO3) wanda ke samuwa lokacin da carbon dioxide ya narke cikin ruwa. Yana da wani fili wanda ya ƙunshi hydrogen, carbon, da oxygen, kuma yana da alhakin ɗanɗanon ɗanɗanon acidic na ruwa na carbonated. Carbonic acid kuma shine muhimmin tsaka-tsaki a cikin zagayowar carbon na halitta, kuma yana taka rawa a yanayin yanayin duwatsu da buffering na pH na teku.