Each entry in the database is a cluster of surnames. These clusters comprise a title and a list of surnames. The surnames are in the same cluster by virtue of their lexical relationship to the main Irish-language form of the surname. The title is the personal name from which the surname cluster is derived. Each surname is classified by language (Irish or English), and by status (primary, historical, alternative). Each Irish-language surname contains one base form as well as all of its inflected forms. The inflected forms are derived algorithmically from the base form. English-language surnames do not have inflected forms.