salary increase vs wage hike

salary increase and wage hike both are nouns.

Word	Noun	Adjective	Verb	Adverb
salary increase	Yes	No	No	No
wage hike	Yes	No	No	No

As nouns, salary increase and wage hike are synonyms defined as:

Other synonyms of salary increase include hike, raise, rise, wage increase.

salary increase (noun)	wage hike (noun)
the amount a salary is increased	the amount a salary is increased