ordinal number vs no.

ordinal number and no. both are nouns.

Word	Noun	Adjective	Verb	Adverb
ordinal number	Yes	No	No	No
no.	Yes	No	No	No

As nouns, ordinal number and no. are synonyms defined as:

ordinal number and no.: the number designating place in an ordered sequence

Other synonyms of ordinal number include ordinal.

ordinal number (noun)	no. (noun)
the number designating place in an ordered sequence	the number designating place in an ordered sequence