28th vs twenty-eighth

28th and twenty-eighth both are adjectives.

Word	Noun	Adjective	Verb	Adverb
28th	No	Yes	No	No
twenty-eighth	No	Yes	No	No

As adjectives, 28th and twenty-eighth are synonyms defined as:

28th and twenty-eighth: coming next after the twenty-seventh in position

28th (adjective)	twenty-eighth (adjective)
coming next after the twenty-seventh in position	coming next after the twenty-seventh in position