Ordinal numbers are used to express the position or order in a sequence. In English the ordinal numbers from 1 to 10 are: first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth. See the equivalents in Portuguese. Note that in Portuguese the ordinal numbers have feminine and masculine forms.
Ordinal Numbers are used to refer to the floors in a building, to place positions in a competition etc.
In the chart below study the pronunciation of the Ordinal Numbers.
In Portuguese the ordinal numbers are not used to express the days of the month. People use the word “primeiro” just for the first day and cardinal numbers (dois, três, quatro, cinco, seis…) for the other days.