characteristic ratio

in polymers
The ratio of the mean-square end-to-end distance, < r 2 > 0, of a linear polymer chain in a theta state to N · L 2, where N is the number of rigid sections in the main chain, each of length L; if all of the rigid sections are not of equal length, the mean-square value of L is used, i.e.
L 2 = ∑ i L i 2 – N
In simple single-strand chains, the bonds are taken as the rigid sections. The recommended symbol is: C N(C ∞ when N → ∞).
Purple Book, p. 49