Nth (adjective)

Used to indicate an unspecified place in a series or sequence of items or events.

Origin:

From latin n-th, from numerus "number".

Examples:

1. The nth digit of pi is 3.
2. The nth term of the sequence is 4.
3. The nth item in the list is missing.
4. The nth prime number is 11.
5. The nth element in the array is 5.