Retention of existing buildings or groups of buildings, landscapes, etc., taking care not to alter or destroy character or detail, even though repairs or changes may be necessary. Sensitive conservation (pioneered by Morris and others connected with the Arts-and-Crafts movement) is concerned to preserve as much original fabric as possible, and make overt what is new and what is old. Conservation does not necessarily mean preservation: it can involve considerable intervention, even much new building, but the key to success is in respecting existing character, and even enhancing it. A conservation area is one designated as of special architectural or historic interest, where all changes should enhance, rather than detract from, its character.
Huxtable (1970, 1986, 1986a)