Sub-circle: Dedicated to particular functions of a company, like marketing and production. The circle a sub-circle exists in is known as its super-circle.

Roles: An element of a traditional job broken down into a task. A marketing circle, for example, can contain roles like social media, advertising, web marketing, and brand development. Every role comes with agreed-upon accountabilities. It's important to note that a role is not representative of a person — a single employee can have many roles, and roles are always subject to change.
Reference
Feloni, R., Jun. 3, 2015, 31, 083, & 1. (n.d.). Here’s how the “self-management” system that Zappos is using actually works. Retrieved November 4, 2016, from http://www.businessinsider.com/how-zappos-self-management-system-holacracy-works-2015-6