The term 'slender one' can be used to describe two different things: a WISP (4 letters) and a sylph (5 letters). A WISP is a small, thin strand of something, such as smoke or fog. It can also refer to a person who is very thin or frail. A sylph is a mythical creature that is often depicted as a slender, beautiful woman with wings. Both terms are used to describe something that is slender or delicate in appearance.