Честотите се дефинират като много чести (> 1/ 10), чести (> 1/ 100, < 1/ 10), нечести (> 1/ 1 000, < 1/ 100), редки (> 1/ 10 000, < 1/ 1 000), много редки (< 1/ 10 000).
Frequencies are defined as very common (> 1/ 10), common (> 1/ 100 ,< 1/10), uncommon (> 1/ 1000 ,< 1/100), rare (> 1/ 10,000, < 1/ 1000), very rare (< 1/ 10,000).