What term describes the end of a hair strand that forms a complete circle for styles such as pincurls and roller setting?

The term that describes the end of a hair strand that forms a complete circle is "curl." This is particularly relevant in hair design techniques such as pincurls and roller setting, where the hair is wrapped or shaped into circular formations. A curl is defined by its rounded shape, which gives volume and texture to hairstyles.

In contrast, a wave is characterized by a bend or ripple in the hair, but it does not form a complete circular shape like a curl does. A twist refers to a technique where hair is twisted around itself or another section of hair but is distinct from the circular formation of a curl. A spiral, while it may imply a circular motion, generally describes a specific type of curl that is elongated and corkscrew-like in appearance, rather than the foundational circular shape that defines a basic curl. Thus, in the context of hair design techniques, the correct terminology for a complete circular end on a hair strand is indeed "curl."