grammatical vs well-formed

grammatical and well-formed both are adjectives.

Word	Noun	Adjective	Verb	Adverb
grammatical	No	Yes	No	No
well-formed	No	Yes	No	No

As adjectives, grammatical and well-formed are synonyms defined as:

grammatical and well-formed: conforming to the rules of grammar or usage accepted by native speakers

grammatical (adjective)	well-formed (adjective)
conforming to the rules of grammar or usage accepted by native speakers	conforming to the rules of grammar or usage accepted by native speakers
of or pertaining to grammar