Creative Commons licences (CC licences) are part of a licensing model that offers standardised licence agreements. The following four licence modules can be combined according to the modular principle:

• BY: Attribution
  The author of the work must be named (mandatory module).
• NC: Non-commercial
  The work may not be used commercially.
• ND: No derivatives (no derivatives)
  The work may not be modified.
• SA: Distribution under the same conditions (share alike)
  The work may be modified and distributed, but only under the original licence.

This allows six different licence variants to be created - from the CC BY licence as the most permissive to the CC BY-NC-ND licence as the most restrictive licence.