50 atoms,
and not one more

Semantic atoms are an engineering interlingua, not a theory of human cognition.

Solid cells are the 40 Natural Semantic Metalanguage primes (Wierzbicka, Goddard) — established as members of that inventory, not as proven universals. Dashed cells are the 10 additions this dataset needed. The validator caps the inventory at fifty, so it cannot quietly grow into an ontology.