Complex sentence: The unary numeral system (base-1, a non-standard positional numeral system) is the simplest numeral system to represent natural numbers: in order to represent a number "N", an arbitrarily chosen symbol is repeated "N" times.
Split into simpler sentences: The unary numeral system (base-1, a non-standard positional numeral system) is a simple numeral system representing natural numbers. In order to represent a number "N", an arbitrarily chosen symbol is repeated "N" times.