  Let us consider an infinite word and $k\geq 1$ an integer. By steps of $k$,
we substitute a letter ofthis infinite word by the power of an external letter.
The new word obtaining by this process is called $k$ to $k$ substitution of a
power letter. After the application of this new notion on modulo-reccurent
words and in particular on Sturmian words. We establish the complexity function
of those words.
