This root is found in many English words, including:
* Suicide: Taking one's own life (sui + cide)
* Suicidal: Relating to suicide (sui + cidal)
* Sui generis: Unique, of its own kind (sui + generis)
* Suave: Smooth, charming (sui + ave)
There are other Latin roots that can relate to "self" in some contexts, but "sui" is the most common and direct.