In the eighth century CE, in the city of Basra in modern-day Iraq, the scholar al-Khalil ibn Ahmad al-Farahidi compiled Kitab al-'Ayn (كتاب العين), the first dictionary of the Arabic language and one of the earliest known comprehensive dictionaries of any language. This monumental work organized words by their phonetic structure, beginning with the letter 'ayn (ع), and included extensive commentary on their meanings and usage. It established the lexicographical tradition for the Arabic language and influenced Islamic scholarship for centuries.

Kitab al-'Ayn provided the essential lexical foundation for the rich tradition of Arabic poetry, enabling poets to access a vast vocabulary and understand the nuances of classical Arabic. Its systematic organization influenced later Arabic dictionaries and set a standard for lexicography in the Islamic world. The dictionary's emphasis on phonetic roots also facilitated the study of Arabic prosody, directly impacting the formal structure of Arabic verse.