Can anyone help me about the correct usage of nd and th ?
The nth best grade
The n'th best grade
The nnd best grade
What are they called in the grammar ?
Which one of them is grammatically correct ?
Thanks in Advance
They are called ordinal numbers.
The first three always have the -st, -nd & -rd ending:
1st, 2nd & 3rd.
In the same fashion, 21st = twenty-first, 22nd = twenty-second, 23rd = twenty-third, and so on.
For upcoming numbers add -th:
4th, 7th, 14th...
As for the spelling, add -th.
fourth, seventh, fourteenth.
If the number is a multiple of 10, the spelling changes:
30th = thirtieth.