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