Expansion

These are the bases you take in order after your main starting base.

Overview
Expansion is a slang term for a mining base taken outside of your main starting base. These bases are commonly referred to in the numerical order that you build them. The exception is the first base that you take after your main, which is commonly referred to as the Natural, or natural expansion. After that, bases are simply referred to by "third" or "fourth", etc. Casters will reference them by their position on the clock, if it were superimposed over the map, i.e. "the nine o'clock expansion".