Enterprise Architecure is a so wide argument which is difficult to be defined.
“Enterprise Architecture is a rigorous description of the structure of an enterprise and its technology, which comprises enterprise reusable technology components (business entities), and the externally visible properties of those reusable technology components, and the relationships (e.g. the behaviour) between them”.
…“EA describes the terminology, the composition of enterprise components, and their relationships with the external environment, and the guiding principles for the requirement (analysis), design, and evolution of an enterprise. This description is comprehensive, including enterprise goals, business process, roles, organizational structures, organizational behaviours, business information, software applications and computer systems.” (Wikipedia)
“Enterprise Architecture is the process of translating business vision and strategy into effective enterprise change by creating, communicating and improving the key requirements, principles and models that describe the enterprise’s future state and enable its evolution.
The scope of the enterprise architecture includes the people, processes, information and technology of the enterprise, and their relationships to one another and to the external environment. Enterprise architects compose holistic solutions that address the business challenges of the enterprise and support the governance needed to implement them. (Gartner)
An Enterprise Architecture contains both a Business view and an IT view: