Recurrence Relation

Where a number is calculated from numbers before it in a sequence.

Example: the factorial function has each number calculated from the previous number in this way:

n! = n(n-1)!

So 10! = 10 x 9!, and 9! = 9x8!, down to 1!=1

The Fibonacci Sequence is another example.

In English "recur" means to occur again (and again)