IPA: /ɒnˈtɒlədʒɪst/
KK: /ɑnˈtɑlədʒɪst/
A person who studies the nature of being, existence, or reality, often focusing on the categories of being and their relations.
The ontologist presented a fascinating theory about the nature of existence.
Ontologist → It is formed from "onto-" (from Greek "ontōs", meaning being or existence) and "-logist" (from Greek "logistēs", meaning one who studies). An ontologist is someone who studies the nature of being or existence.
Think of someone who studies 'being' ('onto-') — that's what an ontologist does.