class vs senior class

class and senior class both are nouns.

Word	Noun	Adjective	Verb	Adverb
class	Yes	No	Yes	No
senior class	Yes	No	No	No

As nouns, senior class is a hyponym of class; that is, senior class is a word with a more specific, narrower meaning than class:

Other hyponyms of class include graduating class, junior class, sophomore class, freshman class.

class (noun)	senior class (noun)
education imparted in a series of lessons or meetings	final grade or class in high school or college
elegance in dress or behavior
a collection of things sharing a common attribute
people having the same social, economic, or educational status
(biology) a taxonomic group containing one or more orders
a body of students who are taught together
a body of students who graduate together
a league ranked by quality

class (verb)	senior class (verb)
arrange or order by classes or categories