- Who is: Xun Zi in Philosophy
- Who is: Xenophanes in Philosophy
- What it is: Existentialism (due to its origin with “Ex” in some languages) in Philosophy
- What is it: Xeno's Paradoxes in Philosophy
- What is it: Xenodochia in Stoicism (hospitality, a Stoic value)
- What is it: Woodcut in Stoicism (as a form of contemplative artistic expression)
- What it is: Check in Stoicism (referring to a state of checking or challenging)
- What is it: Xenophobia in Stoicism
