An enlightened person is called an Arahat (Arahant). They are not Buddhas. The Buddha is one person in one world-system who rediscovers the Dhamma (Dharma) after it has been lost. Often a Buddha goes on to teach that Dhamma, but there are certain Buddhas who arise who never teach. These are called Paccekka Buddhas.

It's still possible to look at a Chinese text and determine accurately whether an English translation should mark definiteness or indefiniteness on particular nouns. That wouldn't be possible if the distinction didn't make sense.