reading morphologically

A resource for using morphophonology in Ancient Greek and Latin language instruction.

The Double Dental Rule

Introduction

When two dentals combine, σ is inserted between them and the first dental drops:

          πιθ/τό/ς > πιθστός > πιστός

Intermediate

When the combination of a base and a marker results in two adjacent dental stops, σ is inserted between them. For instance:

          πε/πυθ/ται > πέπυθσται > πέπυσται

Expectedly, the first dental drops before the sigma.

The Double Dental Rule helps explain why dental stops become σ before μ. See the following chart of the perfect middle/passive indicative singular, and solve for x:

1st Personπε/πυθ/μαιx
2nd Personπε/πυθ/σαιπέπυσαι
3rd Personπε/πυθ/ταιπέπυσται

In the 2nd person πέπυσαι and the 3rd person πέπυσται, it appears that the base πυθ/ becomes πυσ/. Thus when we solve for x πε/πυθ/μαι produces πέπυσμαι.

The same occurs in Latin, but in a following step the second dental assimilates:

          ced/tum > cedstum > cestum > cessum