По честота се определят като много чести (≥ 1/ 10), чести (≥ 1/ 100 до < 1/ 10), нечести (≥ 1/ 1 000 до < 1/ 100), редки (≥ 1/ 10 000 до < 1/ 1 000) и много редки (< 1/ 10 000).
Frequencies are defined as very common (≥ 1/ 10), common (≥ 1/ 100 to < 1/ 10), uncommon (≥ 1/ 1,000 to < 1/ 100), rare (≥ 1/ 10,000 to < 1/ 1,000), and very rare (< 1/ 10,000).