zepto-

American  

1. a combining form meaning “one sextillionth” (10-21 ).

---

Usage

What does zepto- mean? Zepto- is a combining form used like a prefix meaning “one sextillionth (10-21) .” It is very occasionally used in scientific terms to name units. Zepto- comes from an alteration of the form hepta-, from Greek heptá, meaning "seven." The name is a reference to 10-21, which is equivalent to 1000-7. To learn more, read our Words That Use article on hepta-. The z in zepto- was added as part of a reverse alphabetical paradigm for creating numerical combining forms, along with yocto- (10-24); compare with zetta-, meaning “one sextillion,” by reading our Words That Use article on that form.