Sisasystem

undefined:

A sisasystem is an umbrella term for formalized groups within systems such as subsystems, sidesystems, hemisystems, and sparsystems. This can also be used as a general term when a formalized group doesn't fit into any existing group model or term or chooses not to classify itself.

Etymology
The suffix comes from Finnish “sisällä”, meaning “inner, internal, interior”.

Related Terms
See terms specific to sisasystems.

Layer clusters/metalarachs, metaregna, lavhachruks, and various types of sisasystem clusters (a term which includes the last two, but not layer clusters) are similar terms, but fundamentally different in that they are much looser or more informal/nominal groupings rather than structural or more formal ones.

Clusters and groups are less-formalized groupings of headmates.