I have read many times at many websites the meaning of Ayan (Blessing of God, Gif of Allah. But in Quran mentioned the word Ayyana not Ayan, please guide the correct word or meaning
Answer
The actual word is Ayyaan (أَيَّان), which for simplicity can be written as Ayan. Ayyaana is the same word but with ending harakaat (contextual vowels). To help understand this, the name Muhammad is never mentioned in the Quran as Muhammad, it is always Muhammadun or Muhammadin, depending on the context. But when you take the name out of the context, it loses the ending vowels, so it becomes Muhammad. The same is true for Ayyaana, when you think of the word independently, not in a sentence, it becomes Ayyaan.
The meaning you mentioned is incorrect. For the correct meaning see: Ayan