Definition of period of a decimal representation of a number

Question

I need to define the period of a decimal representation of a number!!

Thanks in advance!!

Answer 1

Period of a decimal representation of a number may be defined in terms of cyclic numbers:

See https://en.wikipedia.org/wiki/Cyclic_number#Relation_to_repeating_decimals for fun details

Answer 2

It's just how many digits in the repeated part i.e. 1.23123123... has period 3