The applied arts are the application of design and decoration to everyday objects to make them aesthetically pleasing. The term is applied in distinction to the fine arts which aims to produce objects which are beautiful or provide intellectual stimulation. In practice, the two often overlap.
Architecture is both the process and the product of planning, designing, and constructing buildings or any other structures. Architectural works, in the material form of buildings, are often perceived as cultural symbols and as works of art. Historical civilizations are often identified with their surviving architectural achievements.
A building, or edifice, is a structure with a roof and walls standing more or less permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes, and functions, and have been adapted throughout history for a wide number of factors, from building materials available, to weather conditions, land prices, ground conditions, specific uses, and aesthetic reasons. To better understand the term building compare the list of nonbuilding structures.
We require from buildings, as from men, two kinds of goodness: first, the doing their practical duty well: then that they be graceful and pleasing in doing it; which last is itself another form of duty.
John Ruskin, The Stones of Venice, Volume I, Chapter II.
Architecture differs from a work of art, which can be displayed in different settings and the subject-matter, form and meaning will remain unchanged. The physicality of any built structure can be altered over time as additions and alterations are made. Moreover, a building or work of architecture can change its function as it meets the different demands of its occupants, although its exterior appearance may be unaltered. And its meaning may change depending on the nature of the context. This reveals some of the problems of interpreting historic architecture from a modern-day perspective as the physical changes and different cultural contexts transform the object.
Dana Arnold, Reading Architectural History (2002), Ch. 1 : Reading the past : What is architectural history?