DevOps is more of an organizational and cultural approach that promotes collaboration and communication between both the engineering and operation teams.
Meanwhile, continuous delivery is an essential factor that contributes to the success of implementing DevOps into the product development workflow. Continuous delivery practices help to make new releases more dull and reliable, and establish a more seamless and shorter process.
The key purposes of DevOps is to effectively combine the Dev and Ops roles, remove all silos and result in business goals independent to continuous delivery practices.
On the other hand, continuous delivery works best when there is already a DevOps process in place. Thus, it amplifies the collaboration and streamlines the unified product development cycle of the organization.