ordinal vs number one

ordinal and number one both are nouns.

Word	Noun	Adjective	Verb	Adverb
ordinal	Yes	Yes	No	No
number one	Yes	No	No	No

As nouns, number one is a hyponym of ordinal; that is, number one is a word with a more specific, narrower meaning than ordinal:

Other hyponyms of ordinal include first, number 1.

ordinal (noun)	number one (noun)
the number designating place in an ordered sequence	a reference to yourself or myself etc.; `take care of number one' means to put your own interests first
	the first element in a countable series
	the first or highest in an ordering or series

ordinal (adjective)	number one (adjective)
being or denoting a numerical order in a series
of or relating to a taxonomic order