tier vs contender

tier and contender both are nouns.

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

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

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

tier (noun)	contender (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