43rd vs forty-third

43rd and forty-third both are adjectives.

Word	Noun	Adjective	Verb	Adverb
43rd	No	Yes	No	No
forty-third	No	Yes	No	No

As adjectives, 43rd and forty-third are synonyms defined as:

43rd and forty-third: the ordinal number of forty-three in counting order

43rd (adjective)	forty-third (adjective)
the ordinal number of forty-three in counting order	the ordinal number of forty-three in counting order