third-year vs next-to-last

third-year and next-to-last both are adjectives.

Word	Noun	Adjective	Verb	Adverb
third-year	No	Yes	No	No
next-to-last	No	Yes	No	No

As adjectives, third-year and next-to-last are synonyms defined as:

third-year and next-to-last: used of the third or next to final year in United States high school or college

Other synonyms of third-year include junior.

third-year (adjective)	next-to-last (adjective)
used of the third or next to final year in United States high school or college	used of the third or next to final year in United States high school or college
	second last