This is a story of long ago. At that time the languages and letters were quite different from ours of today. English is used to represent the languages. But two points may be noted. In English the only correct plural of dwarf is dwarfs, and the adjective isdwarfish. In this story dwarves and dwarvish are used but only when speaking of the ancient people to whom Thorin Oakenshield and his companions belonged. Orc is not an English word. It occurs in one or two places but is usually translated goblin (or hobgoblin for the larger kinds).Orc is the hobbits’ form of the name given at that time to these creatures, and it is not connected at all with ourorc, ork, applied to sea-animals of dolphin-kind.