Definitions for

**"Subbase"**A layer used in a pavement system between the subgrade and the base coarse material.

the lowest molding of an architectural base or of a baseboard

a portion of a base, usually consisting of a single axial polygon.

A collection of open sets is a subbase (or subbasis) for a topology if every non-empty proper open set in the topology is a union of finite intersections of sets in the subbase. If ''B'' is ''any'' collection of subsets of a set ''X'', the topology on ''X'' generated by ''B'' is the smallest topology containing ''B''; this topology consists of the empty set, ''X'' and all unions of finite intersections of elements of ''B''.

A set of open sets is a subbase (or subbasis) for a topology if every open set in the topology is a union of finite intersections of sets in the subbase. The topology generated by a subbase is the smallest topology containing the subbase elements; this topology consists of all finite intersections of unions of elements of the subbase.