Keystone

1.

(The main part or principle, the central wedgeshaped stone at the summit of an arch, locking the others in position) keystone of the arch ថ្មដែលទល់ថ្មឯទៀតកុំអោយធ្លាក់, កូនសោរក្ដោង
Example: Freedom is the keystone of democracy.keystone of the theory មូលដ្ឋាន

2.

(បច្ចេកទេស) មូលដ្ឋាន

1.

The central or topmost stone of an arch. This in some styles is made different in size from the other voussoirs, or projects, or is decorated with carving.