The term "base course" is often used in construction and engineering to refer to the underlying layer of a road or building foundation. Synonyms for this term include "subbase," "foundation course," "groundwork," and "underlying stratum." These terms refer to the layer of material that provides support and stability for the upper layers of construction, such as asphalt or concrete. The choice of terminology may depend on the specific context and industry, but they all essentially refer to the same underlying layer. A solid base course is critical for the longevity and durability of any construction project, making these synonyms important to know for those involved in such endeavors.