Demolition is the science and engineering in safely and efficiently tearing down of buildings and other artificial structures. Demolition contrasts with deconstruction, which involves taking a building apart while carefully preserving valuable elements for reuse purposes.

In the context of physical construction, deconstruction is the selective dismantlement of building components, specifically for reuse, repurposing, recycling, and waste management. It differs from demolition where a site is cleared of its building by the most expedient means. Deconstruction has also been defined as "construction in reverse". Deconstruction requires a substantially higher degree of hands-on labor than does traditional demolition, but as such provides a viable platform for unskilled or unemployed workers to receive job skills training. The process of dismantling structures is an ancient activity that has been revived by the growing fields of sustainable and green building.