ordinal number

Từ điển Oxford Advanced Learner 8th

or·din·al [ordinal ordinals] BrE [ˈɔːdɪnl] NAmE [ˈɔːrdənl] (also ˌordinal ˈnumber) noun
a number that refers to the position of sth in a series, for example ‘first’, ‘second’, etc.
compare ↑cardinal
Derived Word: ↑ordinal

Word Origin:
Middle English (referring to a service book in the Christian church): the noun from medieval Latin ordinale (neuter); the adjective from late Latin ordinalis ‘relating to order in a series’, from Latin ordo, ordin- ‘row, series, rank’.