Software architecture is the process of defining the structures and components of a software system and their interfaces to establish the framework for the development of a computer system. It is an early stage of the system design process and represents the link between specification and design processes. The software architecture of a system describes its major components, their relationships, and how they interact with each other.

Architectural design is the process of creating an architecture. It involves identifying major system components and their communications, and the output of this design process is a description of the software architecture. The use of architectural styles is to establish a structure for all the components of the system.

Software architectures can be designed at two levels of abstraction: high-level architecture and low-level architecture. High-level architecture is concerned with the overall system structure and behavior, while low-level architecture is concerned with the implementation details of individual components.

Some common architectural patterns include the layered pattern, client-server pattern, master-slave pattern, pipe-filter pattern, broker pattern, peer-to-peer pattern, event-bus pattern, model-view-controller pattern, blackboard pattern, and interpreter pattern.

The role of a software architect is to provide a solution that the technical team can create and design for the entire application. They make design decisions related to overall system structure and behavior, and analyze how the system will achieve essential qualities such as modifiability, availability, and security.

In summary, architectural design in software engineering is the process of defining the structures and components of a software system and their interfaces to establish the framework for the development of a computer system. It involves identifying major system components and their communications, and the output of this design process is a description of the software architecture. The role of a software architect is to provide a solution that the technical team can create and design for the entire application.