Ontomasticon is a simple, lightweight ontology and glossary server written in PHP and making use of MariaDB or MySQL.
"The term onomastikón (collection of names, from ὄνομα/ónoma, ‘name’) describes learned works that are not arranged alphabetically but juxtapose synonyms and terms relating to the same semantic field." 
"An ontology is a way of showing the properties of a subject area and how they are related, by defining a set of concepts and categories that represent the subject." 
The page Customising Ontomasticon explains how to modify CSS and PHP templates while maintaining easy code updates.
The page Translating Ontomasticon< describes how to translate the user interafce, user defined content and terms.
See the GitHub repository.
 Brill's New Pauly.
 Ontology (information science). Wikipedia..