Usually inert organic or inorganic materials which are added to plastics, resins or gel coats to vary the properties, extend volume, or lower the cost of the article being produced.
Any material used in conjunction with fiber to construct a sheet of paper or board. Usually added to improve opacity, softness, and/or printability.
Additives used to make a resin less costly. They can be inert or they can alter some properties of the plastic. See Reinforcements.