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." (Brill's New Pauly)
"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." (Ontology, Wikipedia)
Please see ontomasticon.github.io/.