I. (ˈ) ̷ ̷| ̷ ̷yən(t)th adjective
1. : being number one quintillion in a countable series — see number table
2. : being one of a quintillion equal parts into which anything is divided
II. noun
( plural quintillionths -yən(t)s, -n(t)ths)
: one of a quintillion equal parts of anything