Expand provides for query expansion, and is an important feature of the archives search tool.
SEMANTICS relys on prepared sets of plausibly equivalent entries. Typical sets are writing | othography | orthographic | script, or Nyahkur | Nyah Kur | Nyakur | Niakuol | Niakuoll | Nyahkur Petchabun | Chaobon | Chaodon. The current list can be inspected via the see link.
DERIVATIVES uses a machine-generated list (based on Kevin Atkinson's AGID ref. 4) of lemmas and likely derivative forms, e.g. write | wrote | written | writ | writing | writes.
Either semantic or derivational expansions can be inspected in advance with the preview button.