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 | Guatemala, Myanmar, India, Indonesia, Turkey |
| Sei | Myanmar, India, Japan, Indonesia, Turkey |
| Sej | Philippines, Malaysia, India, United States, Indonesia |
| Сей | Kazakhstan, Belarus, Kyrgyzstan, Russia, Ukraine |