The mosque (from the Arabic masjid, meaning "place of prostrations") has been the place of congregational prayer for Muslims since the formation of Islam in 622 CE. It takes on numerous regional styles and varies greatly in size from that of the congregational Friday mosque, called in Arabic masjid al-jamīʿ, in Persian and Urdu (masjid al-jumʿah), or in Turkish (ulu çami), to a simple oratory (masjid), to an outdoor space for large assemblies (musalla) for special times such as Eid festivals.

Formal ritual prayer (ṣalāt)—a sequence of standing, kneeling, and prostration—is one of the "pillars" of Islam. Muslims often pray alone, but the ummah, the community of believers, is basic to the mosque. Since Islam does not distinguish between the spiritual and the secular, the mosque is a center for both. It is the emblematic building of Islam.

For a Muslim the building...