lansoprazole: antacid (trade name Prevacid) that suppresses acid secretion in the stomach
acid: any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt
nucleus: (astronomy) the center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail