Family name Сей (Say 
, Sei 
, Sej 
) , globally, is a widespread last name. The last name Сей is habitual in Myanmar, where it is quite a common surname, Guatemala, and Turkey (explore the name in all countries). Not in comparison with a country's population, the name is most common in India, Myanmar, and Turkey. Also, Сей is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Say | Turkey, Indonesia, Guatemala, Myanmar, India |
| Sei | Japan, Turkey, Indonesia, Myanmar, India |
| Sej | Philippines, Malaysia, Indonesia, United States, India |
| Сей | Kyrgyzstan, Russia, Belarus, Kazakhstan, Ukraine |