This lecture revisits the meaning and purpose of software architecture. It considers the idea that architecture should ‘scream’ about what the application does, rather than the decisions about frameworks used, database, etc. It highlights the architect’s goal of keeping high-level policy separate from low-level details, allowing decisions about the latter to be deferred to later in development, or changed in subsequent versions of the software. It explores how the Hexagonal Architecture and Clean Architecture concepts provide a structure to keep policy separate from details.