tier vs challenger

tier and challenger both are nouns.

Word	Noun	Adjective	Verb	Adverb
tier	Yes	No	No	No
challenger	Yes	No	No	No

As nouns, challenger is a hypernym of tier; that is, challenger is a word with a broader meaning than tier:

Other hypernyms of tier include competition, competitor, contender, rival.

tier (noun)	challenger (noun)
one of two or more layers one atop another	the contestant you hope to defeat
any one of two or more competitors who tie one another
a relative position or degree of value in a graded group
something that is used for tying
a worker who ties something