Proto-Celtic *trīs

→ Breton tri (inherited)

→ Breton teir (mention)

→ Welsh tri (inherited)

→ Welsh tair (mention)

→ Irish trí (inherited)

→ Scottish Gaelic trì (inherited)

→ Manx tree (inherited)

→ Cornish tri (inherited)

→ Cornish try (inherited)

→ Latin Tricasses (derived)

→ Old Irish trí (inherited)