Why is the word "also" (أيضًا) never mentioned at all in the Holy Quran?

The Holy Quran is not a linguistic dictionary, so it does not contain all the vocabulary or material of the Arabic language, even though it was revealed in a clear Arabic tongue. Some Arabic words, such as the word "أيضًا" (also), may not be found in it, despite its eloquence and its occurrence in the noble Prophetic Hadith, where its meaning is "رجوعًا" (returning/again).