Използват се следните термини за честотата: 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).
The following terms and frequencies are applied: very common (≥ 1/ 10), common (≥ 1/ 100 to < 1/ 10), uncommon (≥ 1/ 1000 to < 1/ 100), rare (≥ 1/ 10,000 to < 1/ 1000), and very rare (< 1/ 10,000).