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." 
Please see the installation page for instructions on installing Ontomasticon on your own server.
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..