معجم العين is a comprehensive Arabic dictionary that is considered the first organized dictionary for the Arabic language. The dictionary was written by Al-Khalil ibn Ahmad Al-Farahidi, who completed it and arranged it in alphabetical order. The dictionary is based on the pronunciation of letters from the deepest point in the throat, through the movements of the tongue and ending at the edges of the lips. Therefore, the first letter is "al-'Ayn" and the last letter is "al-Mim," followed by the guttural letters ("waaw," "yaa," and "hamza").

The dictionary is available on the Android platform and is free to download. It falls under the Education & Reference category and specifically under the Books subcategory. It is a great resource for Arabic speakers and learners, as it contains a vast amount of words and their meanings in the Arabic language.