Why does New Persian contain many Arabic loanwords?

The presence of numerous Arabic loanwords in New Persian is primarily a result of the Islamic conquest of Iran during the 7th century CE. Following this conquest, Arabic became the sacred language of Islam, establishing a period of Arabic hegemony that lasted for three centuries.12

During this time, the proportion of Arabic vocabulary in the Persian language increased significantly, eventually accounting for approximately 40 to 50 percent of its total word material. This linguistic shift occurred as New Persian emerged as a written language in the 9th century, adopting the Arabic alphabet with only minor modifications to accommodate Persian sounds. Despite these changes, New Persian remained closely related to its ancestral forms, such as Middle and Old Persian, while integrating this extensive Arabic influence into its literary and formal traditions.2134