Xinfeng dialect's Ru tone does not change, though in Sidu dialect despite the tone sandhi , it only has one Ru tone.

The evolution of tone IV in other dialects can also be explained in the same way.

Regarding the Mandarin falling tone's vanishing to this day, people have been prone to description through the categories and the evolution rules.

As the Chinese phonetics went into Japanese, the sound of glottal stop emerged.

It is two thousand years since Cantonese have been used by residents in relatively fixed area and closed environment, which is the main reason why entering tone is retained fully in Cantonese.