Well-formed

This is a well-formed vase.

A good translator is one who, akin to a worm, can squirm with delight around in the author's brain mass, and leave through the tongue to have its taste impressions confirmed, and then leave well-formed traces on paper line after line, sheet after sheet, until the last page is done — and he once again returns to his former self, and as a member of the smallest and least respected low-salary group, signs up yet again to exert his effort for God's representative on earth, the publishers.

Sometimes, it's in the questions, when they're well-formed, that the answers are found.

If the parser says it is good, then it must be well-formed and is part of the language.