Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by function]

Anotations

Scope note:

Fluid that smoothes motion or reduces friction between surfaces. Lubricant occurs in nature as synovial fluid in the joints of vertebrate animals. Various artificial lubricants have been used since prehistory, including mud and animal fat. Since the 19th century, crude oil has become the chief source of lubricants for most applications in industry.