In the present paper, it is shown that the fluctuation of information takes approximately the same shape as that of word length, considered as cost of transmission in natural language, and that this tendency is remarkable at the main components of those two fluctuations.
To confirm our statement, we used the spectral analysis for word length and for FB (Forward and Backward) information which reflects the interrelations among the words. From our experiment, we obtained a favorable result which suggests a explicit linear relation between those two fluctuations.