A mosque is the building where Muslims worship God. Throughout Islamic history, the mosque has been the center of the community and cities have formed around this central building. Nowadays, especially in Muslim countries, there is a mosque on almost every corner; this makes it easy for Muslims to participate in the five daily prayers. In the West, mosques are often integrated parts of Islamic centers that also include teaching and community facilities.
Mosques come in all shapes and sizes; they differ from region to region due to the density of the Muslim population in the area. In the past and today, Muslims have commissioned local craftsmen and architects to design beautiful, magnificent mosques.
However, there are certain characteristics that are common to all mosques. Each mosque has a mihrab, a niche in the wall that faces Mecca, the direction in which Muslims pray. Most mosques have a minbar (or pulpit) from which an Islamic scholar can give a sermon or address.
Other common features are minarets, high towers, from which the community is called to prayer. Minarets are visible from afar and are associated with mosques. There is usually a large rectangular or square prayer room. It often takes the form of a flat roof supported by columns or by a system of horizontal beams supported by architraves. In other common mosque designs, the roof consists of a single large dome on pendentives.  There are usually separate prayer areas with separate entrances for men and women.
Mosques have developed significantly in the past 1400 years. Many have courtyards with decorative pools and fountains that originally provided water for prayer washing. Nowadays, however, more washrooms and toilets are available. Originally simple structures with earthen floors, the floors of today’s mosques are usually covered with plush carpets. They are often with geometric patterns and straight lines that make it easier for Muslims to stand in straight rows when they do their daily prayers.
There are never any pictures of living things or statues in mosques, because in Islam it is forbidden to keep or display such things. At times the interior walls of the mosque are decorated with Quran in Arabic calligraphy or with intricate geometric patterns. These patterns can be made from a variety of materials such as mosaic, stucco, stone, porcelain or wood. The classic patterns are called arabesques, and they have the shape of a radial grid, in which circular and star shapes predominate. The patterns can be two and three dimensional.
Mostly, mosques are cool, calm havens even in dry desert countries. When someone enters a mosque, he or she should leave the hustle and bustle of the material world behind and retreat to the quiet hideaway or sanctuary. Mosques are houses of worship. Men are expected to do the five daily prayers in a mosque in the community. Although women are welcome to pray in the mosque, it is more commendable for them to pray at home. Nevertheless, Muslims are allowed to pray anywhere except in dirty or unclean places like toilets or in cemeteries. The Prophet Muhammad, God’s blessings and peace be upon him, said: „The whole earth is a masjid for me.“ . Masjid is the Arabic word for mosque.
In the literal sense, Masjid means place of prostration. The Arabic word comes from the root „sa-ja-da“, which means to prostrate. When a Muslim’s forehead touches the ground, he or she is close to God. Prayer establishes the link between the believer and his Lord, and prostration symbolizes total submission.
Many people have incorrectly stated that the word mosque is not the translation of Masjid. They claim that the word mosque comes from the Spanish mosquito, and they attribute it to Queen Isabella and King Ferdinand of Spain from the 15th century. However, there is absolutely no connection between the words mosque and mosquito.
The word “mosque” was introduced from French to English in the late 14th or early 15th century. It comes from the French word mosquée from the old French mousquaie. The French in turn was derived from the Italian word moschea from moscheta. The Italians got it either directly from the Arabic word Masjid or from the old Spanish mesquita. 
From this we can see that the translation of the Arabic word Masjid into English mosque, (and in German mosque). A mosque is a house of prayer and a place of prostration. It is a building specially designed and built to worship Allah. There the Muslims stand shoulder to shoulder, united in their love for God and their desire to please Him.
Pendentife are an Islamic contribution to architecture that allows a round dome to be placed over a square space or an oval dome over a rectangular space.
 Sahieh Al-Bukhari. My community means me too.
 The American Heritage Dictionary of the English Language, Fourth Edition; © 2000 Houghton Mifflin Company.
Online Etymology Dictionary, http://www.etymonline.com/m8etym.htm