An Engagement is the commercial and governance container created by a statement of work, retainer, internal charter, or equivalent authorization. A Project is an operational unit of coordinated work within exactly one Engagement.
Engagements authorize work; Projects organize work; Tasks execute work; Deliverables embody outcomes.
Why one engagement may contain many projects
A six-month social retainer may authorize the overall relationship while monthly content programs, a campaign launch, and a quarterly strategy review operate as separate Projects. Each Project can have its own context, schedule, tasks, deliverables, and responsibility.
Keeping the concepts separate prevents contract lifecycle from becoming indistinguishable from day-to-day delivery. It also allows a single Engagement to preserve its commercial history while Projects begin, finish, or change underneath it.