kudos vs congratulations

kudos and congratulations both are nouns.

Word	Noun	Adjective	Verb	Adverb
kudos	Yes	No	No	No
congratulations	Yes	No	No	No

As nouns, kudos and congratulations are synonyms defined as:

Other synonyms of kudos include extolment, praise.

kudos (noun)	congratulations (noun)
an expression of approval and commendation	an expression of approval and commendation