A hierarchy of important ranks

A genus is a rank in the biological classification (or taxonomy). It is above species, and below families. A genus can include more than one species. When biologists talk about a genus, they mean one or more species of animals or plants that are closely related to each other.

As with other taxa, the plural is different from other English words because it is a Latin word. 'Genus' is the singular, and 'genera' is the plural form of the word.