-sun

Suffix

 * 1) Suffix of verb "to be" for subject "you" (informal).

Usage notes

 * It's used when the word's last vowel is one of "o" or "u".
 * It could be "-sün", "-sin", "-sın" according to the last vowel of the word.
 * While talking about you (plural) or you (formal), it becomes "-sunuz"