Noun
tribus (plural tribus or tribuses)
(taxonomy) Synonym of tribe
However, in both writing and inscriptions, the tribus is found with much less frequency than other parts of the name; so the custom of including it does not seem to have been deeply ingrained in Roman practice. Source: Internet
Precisely when it became common to include the name of a citizen's tribus as part of his full nomenclature is uncertain. Source: Internet
Geography was not the sole determining factor in one's tribus; at times efforts were made to assign freedmen to the four urban tribes, thus concentrating their votes and limiting their influence on the comitia tributa. Source: Internet