Ontological (adjective)

1. Relating to the branch of metaphysics concerned with the nature of being and existence.
2. Relating to the nature of existence or being as such.

Origin:

Late 17th century: via latin from greek ontologos "concerned with being" (from ont- "being" + -logos "study of").

Examples:

1. Ontological arguments for the existence of God.
2. An ontological question is one concerning the nature of existence.
3. The ontological status of the self is a topic of debate among philosophers.
4. The ontological nature of the universe is a complex and mysterious topic.
5. He ontological difference between humans and animals is a subject of much discussion.