Coa may refer to:
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams.
Coagulation (also known as clotting) is the process by which blood changes from a liquid to a gel, forming a blood clot.
Coaxial cable, or coax (pronounced /ˈkoʊ.æks/), is a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield.
Coal mining is the process of extracting coal from the ground. Coal is valued for its energy content, and, since the 1880s, has been widely used to generate electricity.
A coat of arms is an heraldic visual design on an escutcheon (i.e. shield), surcoat, or tabard. The coat of arms on an escutcheon forms the central element of the full heraldic achievement which in its whole consists of shield, supporters, crest, and motto.
Coaching is a form of development in which a person called a coach supports a learner or client in achieving a specific personal or professional goal by providing training, advice and guidance.
China is the largest producer and consumer of coal in the world and is the largest user of coal-derived electricity, generating an estimated 73% of domestic electricity production in 2014 from coal.