Following [31], we make use of the following statistics: • #(w bg ) -the number of Bulgarian sentences in the bi-text containing the word w bg ; • #(w ru ) -the number of Russian sentences in the bi-text containing the word w ru ; • #(w bg , w ru ) -the number of corresponding sentence pairs in the bi-text containing the word w bg on the Bulgarian side and the word w ru on the Russian side.
nakov & Pacovski [31] tried various combinations of these statistics; in their experiments, the bestperforming formula was the following one: now, note that we have the following inequalities: having a high number of co-occurrences #(w bg , w ru ) should increase the probability that the words w bg and w ru are cognates.