General Formal Ontology
Top-level ontology integrating objects and processes. Covers time, space, properties, relations, roles, and situations.
Visit WebsiteBrowse the tree, filter it, or click any class to see just its corner of it.
Where this one tends to earn its keep.
Biomedical data integration
Clinical information modeling
Philosophical knowledge representation
Process-oriented domain modeling
I haven't checked this label against the actual licence text — it's the catalogue's original guess. Check the ontology's own site before you rely on it.
Others worth a look in Foundational.