The term 'Sphere of Competition' can be summed up by the word 'ARENA', which is a 5 letter word. An ARENA is a large, enclosed area used for sports and other forms of entertainment. It is typically an oval or circular shape, and is often used for events such as concerts, boxing matches, and other sporting events. The term 'Sphere of Competition' is often used to refer to any type of competitive environment, such as a business or political ARENA.