Final answer:
The Ismaili faith spread to other countries mainly through trade routes and missionary activities, with merchants and religious scholars establishing Islamic institutions in diverse areas, thus contributing to the spread of the religion and associated languages like Arabic and Persian.
Step-by-step explanation:
The Ismaili faith, a branch of Islam, spread to other countries predominantly through trade routes and missionary activities. Trade routes crisscrossed the Islamic world and provided a network for not just the exchange of goods but also for cultural and religious ideas. Muslim traders would venture into various parts of the world, including East and West Africa, India, Southeast Asia, and along the Silk Roads connecting the Middle East with China. Through these interactions, they intermarried with local populations, established mosques, schools, and charitable organizations, further rooting Islam in these communities.
Moreover, religious scholars and missionaries followed merchants into new areas to establish Islamic religious institutions. This not only facilitated the spread of the Islamic faith but also contributed to the spread of languages like Arabic and Persian, which became the lingua franca for commerce and scholarship.