"Yok" means not existing Hayır means no Değil means not But in Turkish we can use all of these words like meaning no. It doesn't matter what you use, these words usally give same meanings. :)

I want to give a few example. There isn't any justice in this world. Bu dünyada hiç adalet yok. May i also ask question? -Yes or -No. These are not facts. Bunlar gerçekler değil.

In sentences, which are constructed by one of the different forms of 'to be' instead of a full verb, the word değil 'not' is used to make the sentence negative. Personal suffixes follow degil instead of the adjective or noun. Examples Aç değilim. İ am not hungry Hasta değilsin: You are not sick. Kilim pahalı değil: The rug is not expensive. Hava soğuk değil: The weather is not cold. Yorgun değiliz: We are not tired. Amerikalı değiller: They are not from America. Öğrenci değil: He/she is not student. note: a common mistake in making a noun sentence negative is adding personal suffixes to the adjective or nouns instead of "değıl". Example (Yorgunum değil) "wrong". The correct form is "Yorgun değilim". "değil" is used to make a sentence negative if only the sentence is constructed by one of the forms of "to be". When the sentence has a verb however, "değil" cannot be used. Example: Gidiyorum: I am going. Gidiyorum değil: It doesn't mean "(I am not going). "wrong"

22. To Have and There is / are The meaning of “There is, there are” is conveyed through the word var. It means “there is / it exists”. Otoparkta beş araba var. There are five cars in the parking lot. Bahçemizde üç ağaç var. There are three trees in our garden. To say “There aren’t, there isn’t”, the word yok is used, which means “there isn’t / it doesn’t exist”. Apartmanımızda hiç Amerikalı yok. There are no Americans in our apartment. Saying you have something is fairly easy in Turkish. For this purpose, the possessive suffixes and the word var are used together. Küçük bir kaplumbağam var. I have a (lit. “my”) small tortoise. Sāhilde evi var. He/she has a (lit. “his/her”) house by the seaside. For negation, yok is used in the same way. Kedimiz yok. We don’t have a (lit. “our”) cat. To ask questions like “do you have, don’t you have”, var and yok are used with the question particle, making var mı and yok mu. Arabanız var mı? Do you have a (lit. “your [pl. or formal] car”) car? Bilgisayarları yok mu? Don’t they have a computer of their own?

from my understanding, yok is the opposite of var .. so it is there is and there is not degil is when you say i am not home for example ... ben evde degilim