CON - To study, especially in order to gain knowledge of.
ION - An atom or group of atoms bearing an electrical charge such as the sodium and chlorine atoms in a salt solution.
OIL - Liquid fat.
NIL - Nothing; zero.
AIL - Painful; troublesome.
COAL - A black rock formed from prehistoric plant remains, composed largely of carbon and burned as a fuel.
COIL - Something wound in the form of a helix or spiral.
COIN - A piece of currency, usually metallic and in the shape of a disc, but sometimes polygonal, or with a hole in the middle.
COLA - The kola plant, genus Cola, famous for its nut, or one of these nuts.
ICON - An image, symbol, picture, or other representation usually as an object of religious devotion.
LION - A big cat, Panthera leo, native to Africa, India and formerly to much of Europe. The term may apply to the species as a whole, to individuals, or to male individuals. It also applies to related species like mountain lions.
LOAN - A sum of money or other valuables or consideration that an individual, group or other legal entity borrows from another individual, group or legal entity (the latter often being a financial institution) with the condition that it be returned or repaid at a later date (sometimes with interest).
NAIL - To drive a nail.
LAIN - Past participle of lie (oriented in a horizontal position, situated).
LOIN - The part of the body (of humans and quadrupeds) at each side of the backbone, between the ribs and hips.
OILCAN - A container with a long spout, for containing oil and delivering it in drops or small quantities for lubricating machinery.