Suppose we solve dictionary matching problem for $d$ patterns with the Aho-Corasick algorithm. Then our main data structure consists of a trie with $n$ vertices and auxiliary structures. I want to estimate the dictionary size $d$ via $n$. It seems reasonable that $d = o(n)$, but maybe there is some research, that provides more accurate estimation of dictionary size based on real data.
So, what estimation for $d$ via trie size $n$ fit reality the best?