Keywords: etymology of the words yaz and yay, lexicology, the name of Turkish seasons, Turkish chronology, Turkish historical lexicology
During the historical periods of the Turkish language, the use of the words `yaz` and `yay`, which have existed in both historical resources and in some contemporary Turkish dialects, has been noted to be rather complex in historical texts. Even though both `yaz` and `yay` can be traced in the first Turkish language texts, `yaz` was used to refer to the six-month period of the season, whereas `yay` referred only to the summer season. Kashgarli`s Dīvānu LuŞāti't- Türk defines 'yay' as 'spring' while 'yaz' is defined as the 'summer season'. In the texts of the Harezm field, the 'yaz' and 'yay' clarification is more distinctive where 'yaz' is used to define 'the spring season' and 'yay' is used for 'the summer season'. In some of the Kıpchak resources, similar to the definitions in Dīvānu LuŞāti't- Türk, 'yay' means 'spring' and 'yaz' refers to 'the summer season'. Yet, Old Turkish Anatolian resources usually define 'yaz' as both 'spring' and 'summer', while it is possible to view the distinction between 'yay' and 'yaz' in some texts. In relation to its historical development, the word 'yaz' has preserved its position in the Turkish of the Ottomans and Turkey, while the word 'yay' has lost its use in the aforementioned Turkish. Thus 'yaz' has replaced the use of 'yay' and the word 'yaz' has lost its use, being replaced by the Turkish + Persian compound 'ilkbahar'