The term 'consisting of a single element' can be described as unary, which is a five-letter word. Unary is an adjective that describes something that consists of one element or part. It is often used in mathematics and computer science to describe operations that involve only one operand or argument. For example, a unary operation might involve adding one to a number or multiplying it by two. Unary can also be used to describe a set that contains only one element.