Existential sentences express the existence or non-existence of something, typically translated as "there is/are" or "there isn't/aren't." Turkish uses the words var (exists, there is/are) and yok (doesn't exist, there isn't/aren't).

1. Var (There is / There are / Exists / Has/Have):

Var indicates existence or possession.

• Simple Existence:
  Masada kitap var. (There is a book on the table.)
  Sorun var mı? (Is there a problem?)
• Possession (with Genitive + Possessive Suffix):
  Benim arabam var. (I have a car. - Lit. "My car exists.")
  Onun iki kardeşi var. (He/She has two siblings.)

2. Yok (There isn't / There aren't / Doesn't exist / Doesn't have):

Yok indicates non-existence or lack of possession. It is the direct negative counterpart to var.

• Simple Non-Existence:
  Masada kitap yok. (There isn't a book on the table.)
  Hiç sorun yok. (There is no problem at all.)
• Lack of Possession:
  Benim arabam yok. (I don't have a car.)
  Vaktim yok. (I don't have time. - Lit. "My time doesn't exist.")

Tenses and Moods with Var/Yok:

Var and yok can be combined with the past tense suffix (-dı/-di) or conditional (-se/-sa) by using the copula i- (which is often invisible in present but appears in other tenses).

• Evde kimse var mıydı? (Was there anyone at home?) (var + i + di)
• Param yoktu. (I didn't have money.) (yok + i + du)
• Zamanın varsa, konuşalım. (If you have time, let's talk.) (var + i + sa)

Var and yok are fundamental for expressing many common ideas in Turkish.