1. A guide, standard, indicator, symbol, or number denoting a relationship with respect to size, capacity, or function, of one part or thing to another. 2. A core or mold used to record or maintain the relative position of a tooth or teeth to one another and/or to a cast. 3. A guide, usually made of plaster, used to reposition teeth, casts, or parts. 4. In epidemiology, a rating scale.