text: For each amino acid in a gene, the weight of each of its codons represented by a parameter termed relative adaptiveness (), is computed from a reference sequence set, as the ratio between the observed frequency of the codon  and the frequency of the most frequent synonymous codon  for that amino acid.
  The CAI of a gene is simply defined as the geometric mean of the weight associated to each codon over the length () of the gene sequence (measured in codons).